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Last Updated :2024/10/09

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Master

Affiliation (Master)

  • Faculty of Engineering　Materials Science and Engineering　Materials Design

Affiliation (Master)

  • Faculty of Engineering　Materials Science and Engineering　Materials Design

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Profile and Settings

Degree

  • Dr of Eng., Tokyo Institute of Technology, 1991（Tokyo Institute of Technology）

Profile and Settings

  • Name (Japanese)

    Miura

  • Name (Kana)

    Seiji

  • Name

    200901097929571241

Achievement

Research Interests

  • 高温強度   3元系状態図   耐熱合金   シリサイド   ニオブ   球状化   めっきプロセス   共析分解   グラフ理論   ナノ材料   強度   反応経路図   一方向凝固   共晶凝固   靭性   金属間化合物   機械的性質   組織制御   合金設計   フェーズフィールド法   クラスター変分法   L1_2型金属間化合物   単結晶合金   Ni_3Al   その場測定法   液体超急冷   微細複合組織   Al_3Ti   実用ニッケル基超耐熱合金   金属薄膜積層体   複合材料   強度・靭性   状態図   metal thin layer   composites   alloy phase diagram   Strengthening and toughnening of materials   

Research Areas

  • Nanotechnology/Materials / Material fabrication and microstructure control
  • Nanotechnology/Materials / Composite materials and interfaces
  • Nanotechnology/Materials / Structural and functional materials
  • Nanotechnology/Materials / Metallic materials

Research Experience

  • 2013/12 - Today Faculty of Engineering, Hokkaido University Division of Materials Science and Engineering Professor
  • 2007/04 - 2013/11 Hokkaido University Associate Professor
  • 1997/04 - 2007/03 Hokkaido University Graduate School of Engineering, Division of Materials Science and Engineering
  • 1987/04 - 1997/03 東京工業大学助手（精密工学研究所熱処理工学部門） 助手
  • 1987 - 1997 Research Associate,1987-1997 Research associate, Precision and Intelligence Lab., Tokyo Institute of Technology

Education

  • 1985/04 - 1987/03  Tokyo Institute of Technology  Graduate School, Division of Integrated Science and Engineering
  • 1981/04 - 1985/03  Tokyo Institute of Technology  School of Engineering  Dept. of Metallurgical Engineering
  •        - 1985  Tokyo Institute of Technology  Faculty of Engineering

Committee Memberships

  • 2020/04 -2023/04   Japan Institute of Metals and Materials   Vice-president

Awards

  • 2019/09 日本金属学会 論文賞
     
    受賞者: 三浦 誠司
  • 2018/09 The Japan Institute of Metals and Materials Significant Contribution Award
     
    受賞者: Seiji Miura
  • 1995/12 日本金属学会 ポスター賞
     
    受賞者: 三浦 誠司
  • 1995/12 The Japan Institute of Metals Young Researcher Award
     力学特性部門 
    受賞者: Seiji Miura
  • 1992/05 本多記念会 Honda Memorial Young Researcher Award
     
    受賞者: Seiji Miura

Published Papers

  • Johtaro MURAOKA, Ken-ichi IKEDA, Seiji MIURA, Koji MORITA, Tohru S. SUZUKI, Yoshio SAKKA
    Journal of the Japan Society of Powder and Powder Metallurgy 71 (7) 257 - 262 0532-8799 2024/07/15
  • Yuji Shirakami, Ken-ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka
    Journal of the Japan Institute of Metals and Materials 88 (7) 129 - 136 0021-4876 2024/07/01
  • Takuya Hashimoto, Ken-ichi Ikeda, Seiji Miura
    MATERIALS TRANSACTIONS 64 (8) 1959 - 1968 1345-9678 2023/08/01
  • Toshiaki Horiuchi, Konatsu Yamada, Shigeru Saito, Ken-ichi Ikeda, Seiji Miura, Frank Stein
    MATERIALS TRANSACTIONS 64 (7) 1622 - 1630 1345-9678 2023/07/01
  • Yuji Shirakami, Ken-ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka
    MATERIALS TRANSACTIONS 64 (4) 805 - 812 1345-9678 2023/04/01
  • Yuji Shirakami, Ken-ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka
    MATERIALS TRANSACTIONS 64 (3) 650 - 656 1345-9678 2023/03/01
  • Daiki Matsui, Koji Morita, Daisuke Terada, Ken-ichi Ikeda, Seiji Miura
    Materials Transactions 63 (7) 1055 - 1064 1345-9678 2022/07/01 [Refereed]
     
    Kink formation and kink strengthening mechanisms were examined in the polycrystalline Ti3SiC2 MAX phase prepared by a reaction sintering process using a spark-plasma-sintering machine. The creep behavior tested by compression at 1200°C showed two deformation regions depending on the applied stresses; at stresses lower than 120 MPa, the stress exponent n exhibited μ1.8, whereas at higher stresses, it exhibited n 2 6. The creep behavior can be ascribed to grain boundary sliding mechanisms for the lower stresses with n μ 1.8 and to dislocation-related creep mechanisms for the higher stresses with n 2 6. The kink bands were frequently observed to form in the grains deformed only at the higher stresses when its basal plane was inclined by about 1020° against the compressive axis. This suggests that the kink bands might be formed only when two factors of the high stresses acting on the basal plane and the resultant dislocation activities were satisfied. Nanoindentation tests conducted around the formed kink bands showed that the nanohardness linearly changed with the distance from the kink bands and showed higher values around the kink bands. Since the kink bands blocked the slip line caused by the nanoindentation, those become obstacles against the dislocation motion caused by the indentation deformation. This suggests that the kink bands would contribute to improving the mechanical properties of the Ti3SiC2 MAX phase.
  • Nana Hashimoto, Ken-ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka
    MATERIALS TRANSACTIONS 63 (2) 133 - 140 1345-9678 2022/02/01
  • Daiki Matsui, Koji Morita, Daisuke Terada, Ken-ichi Ikeda, Seiji Miura
    Journal of the Japan Institute of Metals and Materials 85 (12) 439 - 448 0021-4876 2021/12/01
  • Nana Hashimoto, Ken-ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka
    Journal of the Japan Institute of Metals and Materials 85 (7) 256 - 263 0021-4876 2021/07/01 [Refereed]
  • Syuki Yamanaka, Ken-ichi Ikeda, Seiji Miura
    JOURNAL OF MATERIALS RESEARCH 36 (10) 2056 - 2070 0884-2914 2021/05 [Refereed][Invited]
     
    The effects of Ti and Si addition on the phase equilibrium and mechanical properties of the equiatomic CoCrFeMnNi high entropy alloy (Cantor alloy) were investigated. The phase equilibrium at 1000 degrees C was determined from the result of X-ray diffraction and electron probe micro-analysis. Ti addition stabilizes the sigma phase, A12 phase and C14-Laves phase, while Si addition stabilizes the A13 phase. The phase relationships were represented by projection onto (Co, Fe, Mn, Ni)-Cr-X(Ti or Si) isothermal ternary cross-section at 1000 degrees C in Co-Cr-Fe-Mn-Ni-X senary system. Tensile tests were conducted on Cantor-based fcc single solid solution alloys with Ti or Si dissolution at room temperature. The 0.2% yield strength and ultimate tensile strength increased with either element addition. The Ti-added alloy showed higher strength than the Si-added alloy. The difference in ductility in the alloys is related to their strain hardening behavior in the higher strain range.
  • Ruxia Liu, Masakazu Tane, Hajime Kimizuka, Yuji Shirakami, Ken-ichi Ikeda, Seiji Miura, Koji Morita, Tohru S. Suzuki, Yoshio Sakka, Lianmeng Zhang, Tohru Sekino
    Journal of the European Ceramic Society 41 (4) 2278 - 2289 0955-2219 2021/04 [Refereed]
     
    The elastic properties of a single-crystalline Ti SiC MAX phase with a nanolayered crystal structure, comprising Ti-Si and two distinct Ti-C bonding layers, that had remained unclear because of the difficulty in growing large single crystals, were studied. Rather than unavailable large single crystals, polycrystalline samples with a crystallographic texture were prepared. By analyzing the polycrystalline elastic constants on the basis of an inverse Voigt–Reuss–Hill approximation, the elastic properties of a single crystal Ti SiC with a hexagonal symmetry were determined. This revealed that the single-crystalline Young's modulus was almost isotropic despite its highly anisotropic layered structure. The shear modulus for (0001)〈112¯0〉 was higher than that for {112¯0}[0001] in contrast to the basal slip-dominated plastic deformation reflecting the layered structure. Furthermore, first-principles calculations revealed that heterogeneous interlayer elastic deformation caused by the stabilization of Ti-Si bonding is the origin of the elastic isotropy in a Ti SiC MAX phase. 3 2 3 2 3 2
  • Hashimoto, T, Ikeda, K, Miura, S
    JOURNAL OF THE JAPAN INSTITUTE OF METALS AND MATERIALS 85 (1) 7 - 16 0021-4876 2021/01 [Refereed][Not invited]
  • Yuji SHIRAKAMI, Ken-ichi IKEDA, Seiji MIURA, Koji MORITA, Tohru S. SUZUKI, Yoshio SAKKA
    Journal of the Japan Society of Powder and Powder Metallurgy 67 (11) 607 - 614 0532-8799 2020/11/15 [Refereed]
     
    In order to clarify plastic deformation behavior and mechanism of fracture energy absorption of Ti3SiC2, Vickers indentation tests were conducted for Ti3SiC2 sintered bodies with various textured orientations. Textured Ti3SiC2 sintered bodies were fabricated by slip casting in a strong magnetic field and spark plasma sintering (SPS), and their orientation distribution were analyzed by SEM/EBSD. It was found that for the textured Ti3SiC2, the plastic deformation behavior around Vickers indents such as an indent shape and a grain pile-up were strongly affected by basal slip and kink deformation. Furthermore, the fracture energy absorption mechanism around the indents also depended on the texture orientations. From our results, it is concluded that the most effective factor for suppressing the crack propagation was the grain pile-up, and the second one was crack deflections.
  • 新たなin situ圧子圧入法としての改良型顕微インデンテーション法の開発と応用
    峯田才寛, 三浦誠司, 岡和彦, 宮島達也
    Journal of the Japan Institute of Metals and Materials 84 (4) 128 - 134 2020/04 [Refereed][Not invited]
  • Takuya Hashimoto, Ken-ichi Ikeda, Seiji Miura
    MATEC Web of Conferences 326 03002 - 03002 2020 
    Nanoindentation tests were conducted near the grain boundary (GB) of the Al-Mg-Si alloy, and the influence of GB character on the aging precipitation behavior and the mechanical properties was confirmed. After obtaining the GB characters by electron back scattered diffraction (EBSD) analysis, nanoindentation tests were carried out on under-aged, peak-aged, and over-aged samples. And then, the indentation areas were observed by back scattered electrons imaging (BSE) in order to identify indentation positions with respect to the GB. In this study, for the GB character, focusing on the rotation angle, the high-angle GB (HAGB) and the low-angle GB (LAGB) were selected. In addition, coincident site lattice GBs (CSL) were selected as the special GB. In the 180°C under-aged samples, the nano-hardness near GB is higher than that far from GB, while 180°C peak-aged samples, the nano-hardness is lower than that far from GB. Then the range near the GB where the hardness changes was larger at HAGB than at LAGB and CSL3. This suggests that the GB character affects the aging precipitation behavior and mechanical properties.
  • Kazuki Masaoka, Tadayuki Yamada, Toshiaki Horiuchi, Takaomi Itoi, Seiji Miura
    MATERIALS TRANSACTIONS 61 (5) 849 - 855 1345-9678 2020 [Refereed][Not invited]
     
    Mg alloys with a long-period stacking-order (LPSO) phase are categorized into two types. Those in which the LPSO phase forms in as-cast state are referred to as Type I, while those in which the LPSO phase does not appear until a heat treatment is performed are categorized as Type II. However, the reason that gives rise to these two types of alloy is still not well understood. In the present study, in an attempt to clarify this issue, three different Mg-85(Al,Zn)(6)Gd-9 quaternary alloys were prepared. The alpha-Mg, Al2Gd, Mg3Gd and LPSO phases were identified in the as-cast quaternary alloys by microstructural observations, composition analysis and crystal structure analysis using electron probe microanalysis and X-ray diffraction. The results indicated that all the quaternary alloys could be categorized as Type I, even though ternary Mg(85)Al(6)GD(9) and Mg85Zn6Gd9 alloys were Type II. The crystal structure of the LPSO phase in the as-cast alloys is considered to be18R with dilute solute elements, and the fraction of this phase increases with increasing Zn content. The presence of this phase is thought to be the cause of destabilization of the primary Al2Gd phase. It is thus concluded that the relative stability of phases in the vicinity of the LPSO phase is crucial in determining the type of Mg alloy formed.
  • Takahiro Mineta, Seiji Miura, Kazuhiko Oka, Tatsuya Miyajima
    JOURNAL OF THE JAPAN INSTITUTE OF METALS AND MATERIALS 84 (4) 128 - 134 0021-4876 2020 [Refereed][Not invited]
     
    In the present study, a newly established in situ indentation technique by the use of an optically transparent indenter and an immersion liquid, so-called "modified optical indentation microscopy", was applied for an investigation on the plastic deformation behavior of various samples during indentation. In this technique, the gap between the indenter and the specimen surface is filled with the immersion liquid such as silicone oil and kerosene to widely observe the specimen surface during indentation. In the in situ observations by this technique using polycrystalline pure Mg, the occurrence of various plastic deformation mechanisms and the increase of the anisotropic contact area during indentation can be recognized. Moreover, the increase and the decrease of the contact area which is corresponding to superelasticity during indentation were observed by this technique using the TiNi superelastic alloy. The results of the in situ observations were consistent with the analysis results based on the Hertz theory.
  • Li Peng, Satoshi Takizawa, Ken-ichi Ikeda, Toshiaki Horiuchi, Seiji Miura
    INTERMETALLICS 110 106457  0966-9795 2019/07 [Refereed][Not invited]
     
    An experimental study on a part of the Cr-Nb-Mo-Si quaternary phase diagram associated with the NbCr2 Laves phase is conducted. It is found that most of the Si added to 50Cr-30Mo-20Nb alloys is distributed in the NbCr2 Laves phase and that the amount of Mo in the Laves phase increases with increasing Si addition. The Laves phase in Cr-Mo-Nb alloys with higher Si addition is found to be more stable. Electronic structure calculations based on density functional theory are performed to examine the effects of Mo and Si co-doping on the formation enthalpy of NbCr2. It is found that the co-doping effectively increases the stability of the Laves phase. This result is consistent with the effect of the atomic size ratio D-A/D-B on the stability of the AB(2) Laves phase, where D-A and D-B are the average atomic diameters of atoms occupying the A and B sites of the AB(2) structure, respectively.
  • Kazuki Masaoka, Tadayuki Yamada, Toshiaki Horiuchi, Takaomi Itoi, Seiji Miura
    JOURNAL OF THE JAPAN INSTITUTE OF METALS AND MATERIALS 83 (8) 257 - 263 0021-4876 2019 [Refereed][Not invited]
     
    Mg alloys with long period stacking ordered (LPSO) phases are categorized into two types. Mg alloys where the LPSO phase forms in as-cast state are categorized as Type I, while those where the LPSO phase does not appear in as-cast state but forms during heat treatment are categorized as Type H. However, the origin of the formation type of Mg alloys with LPSO phases still remains poorly understood. In the present study, three different Mg-85 (Al, Zn)(6)Gd-9 quaternary alloys were prepared to elucidate the dominant factors that determine the formation type of Mg alloys with LPSO phases. The a-Mg. Al2Gd, Mg3Gd and LPSO phases were characterized in the as-cast quaternary alloys by microstructural observation, composition analysis and crystal structure analysis by using electron probe microanalysis and X -ray diffraction. It indicates that all the quaternary alloys are categorized as Type I even though the original two ternary Mg85Al6Gd9 and Mg85Zn6Gd9 alloys are categorized as Type II. The crystal structure of the LPSO phases observed in the as-cast alloys is considered to be 18R with dilute solute elements. The amount of the LPSO phases in the as-cast state increases with increasing the 7,n content in the alloys. it is considered to be the cause of destabilization of the primary crystallized Al2Gd phase by the addition of Zn and hence relative stabilization of the LPSO phases. It is thus concluded that the relative phase stability in the vicinity of the LPSO phase is considered to be crucial for determination of the formation type of Mg alloys with LPSO phases.
  • Mg-Al-Zn-Gd 4元系合金鋳造まま材におけるLPSO相の生成挙動
    正岡和貴, 山田忠幸, 堀内寿晃, 糸井貴臣, 三浦誠司
    日本金属学会誌 2019 [Refereed][Not invited]
  • Effect of Si addition on the stability of NbCr2 Laves phase with Mo
    Li Peng, Satoshi Takizawa, Ken-ichi Ikeda, Toshiaki Horiuchi, Seiji Miura
    Intermetallics2017 2019 [Refereed][Not invited]
  • Syuki Yamanaka, Ken-ichi Ikeda, Seiji Miura
    MRS ADVANCES 4 (25-26) 1497 - 1502 2059-8521 2019 [Refereed][Not invited]
     
    It is well known that various elements substitute for a certain sub-lattice of intermetallic compounds. There have been various experimental investigations of the effects of substituted elements on mechanical properties, however. there are few reports describing the effects of multi-element substitution. In the present study, L1(2)-type compounds A(3)B (Ni3Al and Co-3(Al,W)) were selected as model compounds because their substitution behavior is well known. It was reported that various elements such as Ni, Co, Cu, Pd and Pt occupy the A-site, whereas Al, Si, Ga, Ge, Ti, V, Nb, Ta, Mo, and W occupy the B-site. These elements are expected to introduce local lattice distortion, which may affect the motion of dislocations over a wide range of temperatures. Several alloys composed of five or more elements including Ni, Co, Al, Mo, and W, were prepared using an Ar-arc melting machine and heat-treated. Several alloys were found to include an (Ni, Co)(3) (Al, Mo, W, ...)-L1(2) compound as a constituent phase. The nano-hardness of these L1(2) phases was higher than that of the high-strength Co-3(Al,W)-L1(2) compound, confirming that multi-element substitution is an effective way to improve the mechanical properties of an intermetallic compound without decreasing the phase stability.
  • Daisuke Goto, Ken-ichi Ikeda, Seiji Miura
    MRS Advances 4 (25-26) 1491 - 1496 2019 [Refereed][Not invited]
  • Takahiro Mineta, Seiji Miura, Kazuhiko Oka, Tatsuya Miyajima
    MATERIALS TRANSACTIONS 60 (8) 1416 - 1422 1345-9678 2019 [Refereed][Not invited]
     
    In the present study, a newly established in situ indentation technique by the use of an optically transparent indenter and an immersion liquid, so-called "modified optical indentation microscopy", was applied for an investigation on the plastic deformation behavior of various samples during indentation. In this technique, the gap between the indenter and the specimen surface is filled with the immersion liquid such as silicone oil and kerosene to widely observe the specimen surface during indentation. In the in situ observations by this technique using polycrystalline pure Mg, the occurrence of various plastic deformation mechanisms and the increase of the anisotropic contact area during indentation can be recognized. Moreover, the increase and the decrease of the contact area which is corresponding to superelasticity during indentation were observed by this technique using the TiNi superelastic alloy. The results of the in situ observations were consistent with the analysis results based on the Hertz theory.
  • Shigeru Saito, Toshiyuki Takashima, Toshiaki Horiuchi, Seiji Miura, Toshio Narita
    MATERIALS TRANSACTIONS 60 (4) 611 - 615 1345-9678 2019 [Refereed][Not invited]
     
    Ternary Nb-Re-Si alloy samples were melted and pulled simultaneously in a tetra-arc furnace and rapidly water-quenched after heat treatment at 1150 degrees C for 1200 h. The microstructures of the samples that had been water-quenched after heat treatment were observed and the Nb, Re and Si concentrations in the constituent phases were measured using an electron probe microanalyzer (EPMA). In the cross-sectional structure of the obtained alloy samples, the lower portion of the pulled part consists of Nb5Si3 and Nb-Re-Si ternary compound phases. By contrast, the upper portion consists of Nb5Si3 and Nb solid solution phases. The Nb solid-solution phase, Nb5Si3 and Nb-Re-Si ternary compound are in equilibrium. It was found that the solubility limit of Si in the Nb solid-solution phase ranges from 0.6 to 1.7 at%, while the solubility limit of Re in the Nb5Si3 phase is 1.3-2.0 at%. The maximum amount of Re in the Nb5Si3 phase in equilibrium with the Nb solid solution is about 0.9 at%.
  • Li Peng, Ken-ichi Ikeda, Toshiaki Horiuchi, Seiji Miura
    MATERIALS TRANSACTIONS 60 (2) 246 - 253 1345-9678 2019 [Refereed][Not invited]
     
    A new three-phase alloy of 50Cr-30Mo-20Nb (at%) was studied based on the Cr-Mo-Nb ternary phase diagram, and was composed of a Cr-rich BCC1 phase, a Mo-rich BCC2 phase and a NbCr2 Laves phase after heat treatment at around 1523K or lower. A supersaturated BCC single-phase solid solution alloy obtained by homogenization at 1973K for 1 h underwent microstructural evolution during heat treatment at 1473 K. Intragranular precipitation of the Cr-rich BCC1 phase occurred, which led to the formation of an alternating BCC1/BCC2 two-phase microstructure through a discontinuous precipitation process, followed by precipitation of the Laves phase at the BCC1/BCC2 interphase boundaries. At a higher temperature of 1523 K, a similar microstructure was observed, with increased BCC decomposition and Laves precipitation rates, while the alloy consisted of BCC and Laves phases at 1773 K. The mechanical properties of alloys heat treated at 1473K for various periods after the solid-solution treatment were also investigated. A maximum fracture strength of 1493 MPa and a minimum hardness of 773 +/- 7 HV were obtained for an alloy aged for 24 h, where the BCC1/BCC2 two-phase microstructure dominated. The Vickers hardness of an alloy aged for 72 h, which had a fine-grained microstructure that included the Laves phase, was 839 +/- 8 HV under a load of 0.5 kgf, and no obvious microcracks were observed.
  • Yoshimi Watanabe, Shingo Gonda, Hisashi Sato, Seiji Miura
    JOURNAL OF MATERIALS PROCESSING TECHNOLOGY 259 320 - 331 0924-0136 2018/09 [Refereed][Not invited]
     
    A novel method (reaction at narrow holes method, RANH method) to fabricate an intermetallic compound fiber / metal matrix composite is proposed. Narrow holes are drilled in the metal matrix A, and then metal fibers B are inserted into these holes. The assembly is heated to elevated temperatures to obtain molten metal B in the holes. Then the reaction between A and B should cause within the narrow holes. During the reaction, intermetallic compound of A,B replaces the metal B keeping its fiber shape embedded in the metal matrix A. In this study, a Ni-aluminides fiber / Ni composite is fabricated by the novel method. Microstructure and mechanical property of these specimens were investigated. To evaluate the reaction during the RANH method, in-situ observation by laser scanning microscope and differential thermal analysis (DTA) were also carried out. From obtained results, effects of swaging treatment and heating condition on these microstructure and mechanical property were discussed.
  • Takahiro Mineta, Seiji Miura, Kazuhiko Oka, Tatsuya Miyajima
    MATERIALS TRANSACTIONS 59 (4) 602 - 611 1345-9678 2018 [Refereed][Not invited]
     
    A newly established in situ Brinell indentation technique was conducted to investigate the plastic deformation behavior of pure Mg and Mg-Y alloy single crystals under complex stress conditions. The deformation morphology on the upper surfaces of the specimen around the indent could not be sufficiently observed using the previously reported in situ indentation methods with an optically transparent indenter due to the refraction of rays at the indenter/air interface. In this study, the gap between the indenter and the specimen surface is filled with immersion liquids such as silicone oil and kerosene. This technique enables observation of the specimen surface during indentation. Application of the in situ Brinell indentation to pure Mg and Mg-Y alloy single crystals revealed that the shape of the indents is not circular but elliptical, even during loading. The aspect ratio of the indents decreases with increasing Y content. Moreover, the occurrence of plastic deformation around the indents and beneath the indenter could be observed during the loading and unloading processes using the in situ Brinell indentation method.
  • Shigeru Saito, Toshiyuki Takashima, Toshiaki Horiuchi, Seiji Miura, Toshio Narita
    JOURNAL OF THE JAPAN INSTITUTE OF METALS AND MATERIALS 82 (11) 409 - 414 0021-4876 2018 [Refereed][Not invited]
     
    Ternary Nb-Re-Si alloy samples were melted and pulled simultaneously in a tetra-arc furnace and rapidly water-quenched after heat treatment at 1150 degrees C for 1200 h. The microstructures of the samples that had been water-quenched after heat treatment were observed and the Nb, Re and Si concentrations in the constituent phases were measured using an electron probe microanalyzer (EPMA). In the cross-sectional structure of the obtained alloy samples, the lower portion of the pulled part consists of Nb5Si3 and Nb Re-Si ternary compound phases. By contrast, the upper portion consists of Nb5Si3 and Nb solid solution phases. The Nb solid-solution phase, Nb5Si3 and Nb-Re-Si ternary compound are in equilibrium. It was found that the solubility limit of Si in the Nb solid-solution phase ranges from 0.6 to 1.7 at%, while the solubility limit of Re in the Nb5Si3 phase is 1.3-2.0 at%. The maximum amount of Re in the Nb5Si3 phase in equilibrium with the Nb solid solution is about 0.9 at%.
  • Li Peng, Ken-ichi Ikeda, Toshiaki Horiuchi, Seiji Miura
    MATERIALS TRANSACTIONS 59 (11) 1706 - 1715 1345-9678 2018 [Refereed][Not invited]
     
    The isothermal sections of the Cr-Mo-Nb ternary phase diagram have been studied. The C15 NbCr2 Laves precipitation behavior in three different alloys has been investigated in the Cr-Mo-Nb ternary system. The orientation relationship (OR) of NbCr2 in BCC matrix among BCC/Laves two-phase alloys and Cr-rich BCC1/Mo-rich BCC2/Laves three-phase alloy is different at 1473 K; OR 1: (011)(BCC) // (111)(C15), [011](BCC) // [110](C15) and OR 2: (411)(BCC) //; [111](C15), // [110](C15) with low lattice mismatch are both observed in Cr-rich alloys #3 (74Cr-16Mo-10Nb) and #2 (50Cr-30Mo-20Nb). OR 3: (011)(BCC) (111)(C15), [111](BCC) // [011](C15) with a lattice mismatch relatively larger than that of OR 1 and OR 2 is only observed in alloy #2, which may be due to the presence of BCC, and BCC2 interphases formed after BCC decomposition. Only discontinuous precipitation is observed at grain boundaries in Cr-lean alloy #1 (42Cr-31 Mo 27Nb) without obvious OR between the BCC matrix and Laves phase.
  • Takuya Yamanouchi, Seiji Miura
    MATERIALS TRANSACTIONS 59 (4) 546 - 555 1345-9678 2018 [Refereed][Not invited]
     
    Phase equilibria among the refractory bcc solid solution (bcc(ss)), B2, and Laves phases in Nb-Cr-NiAl and Nb-V-NiAl isothermal sections were studied with the aim of introducing the NiAl-B2 phase and/or Al-containing Laves phase for improvement of the oxidation resistance of the bcc(ss) phase as an Al reservoir layer for the Al2O3 surface layer. Laves phases appear in a wide composition range in both of the isothermal sections, which prevent equilibration of NiAl-B2 with the Nb-rich bcc(ss) phase. The geometrical model proposed by Edwards was applied to understand the site-substitution behavior of the multi-component AB(2) Laves phase. In the Nb-Cr-NiAl, Nb-V-NiAl, and Nb-Mo-NiAl systems, the site-substitution behavior of the Laves phases could be explained by comparison of the average atomic diameters of NiAl-B2, Cr, V, and Mo.
  • Takahiro Mineta, Seiji Miura, Kazuhiko Oka, Tatsuya Miyajima, Hiroyuki Sato
    The Proceedings of the Materials and Mechanics Conference 一般社団法人 日本機械学会 2017 619 - 621 2017/10 [Refereed][Not invited]
     
    In order to investigate a plastic deformation behavior of Mg single- and poly-crystals under a complex deformation condition, in-situ Brinell indentation, which is referred to as a modified Brinell optical indentation microscopy, using an optically transparent indenter and an immersion liquid is conducted. This method enables to observe the contact area between the specimen and the indenter, and the specimen surface around the contact area during indentation. As the results of the modified Brinell optical indentation microscopy on a Ti-Ni superelastic alloy, it is recognized that not only increasing the contact area during loading process but also decreasing the contact area during unloading process can be observed by this method. Using the modified Brinell optical indentation microscopy on pure Mg single-crystals, it is revealed that the shape of the indents is not circle but elliptic because of difference in the relative activity of each plastic deformation mechanism. Moreover, decreasing the contact area caused by the pseudoelastic behavior during unloading process is not recognized in pure Mg single-crystals. In pure Mg poly-crystals, the elliptic indent shape is observed in each grain, and a large deformation occurs in the vicinity of the grain boundary in order to keep bonding two grains at the grain boundary.
  • Hidetoshi Somekawa, Tomohito Tsuru, Alok Singh, Seiji Miura, Christopher A. Schuh
    ACTA MATERIALIA 139 21 - 29 1359-6454 2017/10 [Refereed][Not invited]
     
    The effect of crystal orientation on incipient plasticity during nanoindentation was investigated by experiments and molecular statics simulation. Pop-in behavior is a result of dislocation activity, and is therefore influenced by crystal orientation. Experimental results using single crystals indicated that indentations on the basal plane had higher pop-in loads and larger pop-in displacements than those on the prismatic plane, an effect also captured by molecular statics simulation. The difference can be traced to the types of activated dislocations, with not only basal but also pyramidal dislocations active for indentations on the basal plane, but only basal dislocations triggered at the first pop-in on the prismatic plane. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
  • Nobuhiro Matsuzaki, Ken-Ichi Ikeda, Seiji Miura, Nobuaki Sekido, Takahito Ohmura
    MRS Advances 2 (26) 1405 - 1410 2059-8521 2017 [Refereed][Not invited]
     
    Al3Nb is known as a high oxidation resistant material, while it is quite brittle. As the fracture toughness of Al3Nb single crystal and its dependence on the composition are not obtained, the micro-sized fracture testing proposed by Suzuki et al. was performed. Al3Nb single crystal micron-order size cantilevers with a chevron-notch were fabricated in a grain of two-phase polycrystalline alloys by using FIB (Focused Ion Beam). From the load-displacement curves during the bending by a nanoindenter, the average value of fracture toughness of Nb-rich Al3Nb is evaluated to be 2.90 MPam1/2, while the fracture toughness of Al-rich Al3Nb is also evaluated to be 2.82 MPam1/2. From this result, the fracture toughness of Al3Nb is less dependent on its Al/Nb ratio. Furthermore the fracture toughness of Al3 (Nb, V) was evaluated to be 2.82 MPam1/2.The fracture toughness of Al3Nb is seemingly insensitive to V addition.
  • T. Yamanouchi, S. Miura, M. Ohno, K. Ikeda
    MRS Advances 2 (25) 1335 - 1340 2059-8521 2017 [Refereed][Not invited]
     
    For the improvement of oxidation resistance of Nb-based alloys, PdAl-B2 is expected as Al reservoir for Al2O3 surface layer because it is in equilibrium with Nbss (bcc) phase. However, PdAl forms cracks during casting caused by B2 -> β' transformation. To suppress B2 -> β' transformation, Rh, Ru and Ir were chosen as additive elements. It is found that bcc / B2 two-phase field in Nb-Pd-Ir-Al system is limited to be small fraction of Ir, while (Pd,Rh)Al-B2 is in equilibrium with bcc solid solution in a wide composition range and addition of Rh prevents occurrence of B2 -> β' transformation. Composition range of (Pd,Ru)Al-B2 in equilibrium with bcc phase is wider than (Pd,Ir)Al-B2 but narrower than (Pd,Rh)Al-B2. Rh and Ru addition are also beneficial for improving eutectic temperature of Nb-bcc / B2 aluminide two-phase alloys.
  • Takahiro Mineta, Seiji Miura, Kazuhiko Oka, Tatsuya Miyajima
    JOURNAL OF THE JAPAN INSTITUTE OF METALS AND MATERIALS 81 (4) 196 - 205 0021-4876 2017 [Refereed][Not invited]
     
    In order to understand a plastic deformation behavior of pure Mg and Mg-Y alloy single. crystals under a complex stress condition, newly established in. situ Brinell indentation was conducted. The deformation morphology on the upper surfaces of the specimen around the indent could not been sufficiently observed by the previously reported in. situ indentation methods using an optically transparent indenter due to refraction of rays at a surface of the indenter. In this study, the space between the indenter and the specimen surface are filled with immersion liquids such as silicone oil and kerosene. This technique enables to observe the specimen surface during indentation. Using in. situ Brinell indentation on pure Mg and Mg. Y alloy single. crystals, it is found that the shape of the indents on them are not circle but elliptic even during the loading. The aspect ratio of the indents decreases with increasing Y content. Moreover, occurrences of plastic deformation mechanisms around and beneath the indent could be observed during loading and unloading process by using the in. situ Brinell indentation method.
  • Phase equilibrium between bcc solid solution matrix, B2 aluminides and Laves phase in Nb-based alloy
    Takuya Yamanouchi, Seiji Miura
    The proceedings of The 9th Pacific Rim International Conference on Advanced Materials and Processing (PRICM9) 784 - 787 2016 [Refereed][Not invited]
  • Fracture toughness of Al3Nb evaluated by micro-size fracture testing
    Nobuhiro Matsuzaki, Seiji Miura
    The proceedings of The 9th Pacific Rim International Conference on Advanced Materials and Processing (PRICM9) 788 - 790 2016 [Refereed][Not invited]
  • The isothermal sections of Mg-Zn-Gd ternary system in the vicinity of LPSO phase
    Futoshi Miyakawa, Seiji Miura, Ken-ichi Ikeda
    The proceedings of The 9th Pacific Rim International Conference on Advanced Materials and Processing (PRICM9) 814 - 817 2016 [Refereed][Not invited]
  • Factors controlling pseudoelasticity of Mg alloys
    Takahiro Mineta, Seiji Miura, Ken-ichi Ikeda
    The proceedings of The 9th Pacific Rim International Conference on Advanced Materials and Processing (PRICM9) 810 - 813 2016 [Refereed][Not invited]
  • Investigation of substitutional behavior of rare-earth elements in LPSO phases
    Seiji Miura, Futoshi Miyakawa, Ken-ichi Ikeda, Toshiaki Horiuchi, Takaomi Itoi, Satoshi Minamoto
    LPSO2016 ORAL - 02  2016 [Not refereed][Not invited]
  • Comparison with the composition dependence of the LPSO poly-types formed in Mg-M-Y (M=Ni, Cu and Zn) ternary alloy systems
    Takaomi Itoi, Takuya Ogaku, Atsushi Seo, Toshiaki Horiuchi, Seiji Miura
    LPSO2016 POS – 04  2016 [Not refereed][Not invited]
  • Deformation and fracture behavior of Ti3SiC2 ceramics by four-point bending test using a thin sheet
    Ken-ichi Ikeda, Seiji Miura
    LPSO2016 POS-23  2016 [Not refereed][Not invited]
  • Satoshi Minamoto, Toshiaki Horiuchi, Seiji Miura
    MATERIALS TRANSACTIONS 56 (10) 60 - 64 1345-9678 2015/10 [Refereed][Not invited]
     
    The Mg-Zn-Y alloy shows excellent mechanical properties which can be achieved by combining LPSO phase (known as X phase) and an icosahedral quasicrystal phase (land Z phases) in Mg solid solution (a phase). Thermodynamic data for the binary/ternary compounds Mg24Y5, X, Wand H have to be critically assessed to obtain accurate information of three-phase equilibrium in order to understand equilibria among these phases. In this research, we focused on developing CALPHAD (CALculation of PHAse Diagrams) thermodynamic database to evaluate phase diagrams for the Mg-Zn-Y system. Especially thermodynamic models for the Mg24Y5, W and H phases have been determined based on crystallographic data. Then thermodynamic parameters have been assessed to yield experimental data from EPMA/WDS, SEM, TEM and X-Ray diffraction.
  • Marta Ziemnicka-Sylwester, Li Gai, Seiji Miura
    Materials and Design 69 1 - 11 1873-4197 2015/03/15 [Refereed][Not invited]
     
    The TiB2-based Fe-matrix cermets with titanium addition (literarily different Ti:B ratio) were fabricated from elemental powders "in situ" using the Self-propagating High-temperature Synthesis method (SHS) under high pressure. The effect of Ti:B ratio on microstructure and phase composition with particular focus on matrix phase were analyzed using X-ray diffraction (XRD) and Wavelength Dispersive Spectroscopy (WDS) for composites with intended 25vol.% and 35vol.% of Fe. Moreover, for composites with 35vol.% of Fe bending strength and compressive strength were investigated. The compressive strength reached maximum value in material with Ti:B atomic ratio of 0.49, which possessed the highest TiB2 content and matrix phase consisting of Fe and Fe2B. However, modulus of rupture (MOR) test indicated that composite with titanium excess (Ti:B atomic ratio of 0.525) was characterized by the highest bending strength, due to successful elimination of Fe2B intermetallics.
  • S. M. Seyyed Aghamiri, H. R. Shahverdi, S. Ukai, N. Oono, K. Taya, S. Miura, S. Hayashi, T. Okuda
    MATERIALS CHARACTERIZATION 100 135 - 142 1044-5803 2015/02 [Refereed][Not invited]
     
    The microstructure of a new Ni-base oxide dispersion strengthened superalloy powder was studied for high temperature gas turbine.applications after the mechanical alloying process. In this study, an atomized powder with a composition similar to the CMSX-10 superalloy was mechanically alloyed with yttria and Hf powders. The mechanically alloyed powder included only the supersaturated solid solution gamma phase without gamma' and yttria provided by severe plastic deformation, while after the 3-step aging, the gamma' phase was precipitated due to the partitioning of Al and Ta to the gamma' and Co, Cr, Re, W, and Mo to the gamma phase. Mechanical alloying modified the morphology of gamma' to the new coherent gamma-gamma' nanoscale lamellar structure to minimize the elastic strain energy of the precipitation, which yielded a low lattice misfit of 0.16% at high temperature. The gamma' lamellae aligned preferentially along the elastically soft [100] direction. Also, the precipitated oxide particles were refined in the gamma phase by adding Hf from large incoherent YAlO3 to fine semi-coherent Y2Hf2O7 oxide particles with the average size of 7 nm and low interparticle spacing of 76 nm. (C) 2014 Elsevier Inc All rights reserved.
  • Takuya Yamanouchi, Seiji Miura
    Materials Research Society Symposium Proceedings 1760 199 - 204 0272-9172 2015 [Refereed][Not invited]
     
    B2 aluminides have a role of Al reservoir for Al< inf> 2< /inf> O< inf> 3< /inf> surface and it is expected to increase oxidation resistance of (Nb,Mo)-bcc< inf> ss< /inf> substrate. For the accumulation of the basic information to design the alloy composed of B2 coating on bcc< inf> ss< /inf> matrix, bcc< inf> ss< /inf> - B2 two-phase field was investigated in the Nb-Mo-Ni-Pd-Al system at 1273 K. It is found that Pd-rich B2-(Ni,Pd)Al phase is in equilibrium with Nb-rich bcc< inf> ss< /inf> phase, while without Pd, the composition range of bcc< inf> ss< /inf> coexisting with B2-NiAl phase is limited to be low Nb.
  • Shiori Suzuki, Nobuaki Sekido, Takahito Ohmura, Seiji Miura
    Materials Research Society Symposium Proceedings 1760 187 - 192 0272-9172 2015 [Refereed][Not invited]
     
    A micro-sized fracture testing method has been applied to investigate fracture toughness of alpha-Nb< inf> 5< /inf> Si< inf> 3< /inf> . Chevron-notched single crystal specimens with a size of 3 × 3 × 15 μm< sup> 3< /sup> were prepared in a grain of polycrystalline alpha-Nb< inf> 5< /inf> Si< inf> 3< /inf> by focused ion beam, FIB, technique. Fracture tests were conducted using a nanoindenter at room temperature and linear load-displacement curves and smooth fracture surfaces were obtained. This fracture behavior was presumed to be brittle fracture similar to bulk alpha-Nb< inf> 5< /inf> Si< inf> 3< /inf> . The average of fracture toughness K< inf> q< /inf> is 3.45 ± 0.29 MPa√m under a small-scale yielding condition.
  • T. Mineta, S. Miura
    Materials Research Society Symposium Proceedings 1741 (January) 47 - 52 0272-9172 2015 [Refereed][Not invited]
     
    In order to understand enhanced mechanical properties of magnesium-yttrium (Mg-Y) alloys, applied stresses which were required to operate independent plastic deformation mechanisms on various stress axes were evaluated. Moreover, for this analysis, mechanical tests including newly-established testing method "pure-shear test" were conducted to evaluate Critical Resolved Shear Stresses (CRSSes) for various plastic deformation mechanisms of Mg-Y solid solution alloy single crystals with various Y concentration. Relatively higher solid solution strengthening of dominant plastic deformation mechanisms such as basal slip and extension twin at room temperature, results in increase in the activation of non-basal slip system. By a simple analysis based on von-Mises criterion with experimental CRSS values, it is revealed that enhanced mechanical properties of Mg-Y alloys might be attributed to the decrease of difference in the activity of plastic deformation mechanisms by Y addition.
  • Thermal stability of Mg-Zn-Y LPSO phases and revised thermodynamic description of the Mg-Zn-Y phase diagram
    Rainer Schmid-Fetzer, Joachim Groebner, Michiaki Yamasaki, Yoshihito Kawamura, Hiroshi Okuda, Seiji Miura, Toshiaki Horiuchi, Jian-Feng Nie
    2015 Mg proceedings EO-3-0372  2015 [Not refereed][Invited]
  • The phase equilibrium in the vicinity of LPSO phase in Mg-Zn-Gd ternary system
    Futoshi Miyakawa, Ken-ichi Ikeda, Seiji Miura, Toshiaki Horiuchi, Satoshi Minamoto
    2015 Mg proceedings 345 - 349 2015 [Not refereed][Not invited]
  • Deformation behavior of LPSO phase in Mg-Zn-Y alloy by four-point bending test using a thin sheet
    K. Ikeda, R. Nishio, H. Gao, S. Hata, H. Nakashima, S. Miura
    2015 Mg proceedings EO-4-1241  2015 [Not refereed][Not invited]
  • Kenji Iseya, Seiji Miura, Tetsuo Mohri
    JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION 35 (6) 788 - 793 1547-7037 2014/12 [Refereed][Not invited]
     
    Two-phase microstructure calculated by Phase Field calculations is perturbed by Gaussian filtration processes to produce a series of deteriorated images. Fourier spectral analysis is, then, performed on the resultant images to derive information of spatial distribution of phases consisting of the microstructure. It is shown that Fourier spectrum is correlated with characteristic length involved in the microstructure. By inverting a particular spectrum peak, one can estimate the spatial distribution of a particular phase.
  • 垂水 良悦, 山賀 英司, 坂口 紀史, 三浦 誠司, 亘理 文夫
    北海道外科雑誌 北海道外科学会 59 (1) 92 - 92 0288-7509 2014/06
  • Seiji Miura, Toru Hatabata, Takuya Okawa, Tetsuo Mohri
    METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE 45A (3) 1136 - 1147 1073-5623 2014/03 [Refereed][Not invited]
     
    To find a new route for microstructure control and to find additive elements beneficial for improving high-temperature strength, a systematic investigation is performed on hypoeutectic Nb-15 at. pct Si-X ternary alloys containing a transition element, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, Pt, or Au. Information on phase equilibrium is classified in terms of phase stability of silicide phases, alpha Nb5Si3, Nb4SiX, and Nb3Si, and the relationship between microstructure and mechanical properties both at room temperature and high temperature is investigated. All the additive elements are found to stabilize either alpha Nb5Si3 or Nb4SiX but destabilize Nb3Si. A microstructure of Nb-ss/alpha Nb5Si3 alloy composed of spheroidized alpha Nb5Si3 phase embedded in the Nb-ss matrix is effective for toughening, regardless of the initial as-cast microstructure. Also the plastic deformation of Nb-ss dendrites may effectively suppress the propagation of longer cracks. High-temperature strength of alloys is governed by the deformation of Nb-ss phase and increases with higher melting point additives.
  • Seiji Miura, Yoshihito Sekito, Takuya Okawa, Takuya Yamanouchi, Tetsuo Mohri
    Materials Science Forum 783-786 1171 - 1175 2014 [Not refereed][Invited]
  • Mitarai(Yamabe) Yoko, HOSODA Hideki
    Journal of Alloys and Compounds Elsevier B.V. 577 (577) 0925-8388 2013/11 [Not refereed][Not invited]
     
    The phase transformation and high-temperature shape memory effect of Ti(Pt, Ir) were investigated. First, the Ti-rich phase boundary of Ti(Pt, Ir) was investigated by phase composition analysis by secondary electron microscopy (SEM) using an electron probe X-ray micro analyzer (EPMA), X-ray diffraction analysis and transmission electron microscopy (TEM). Then, the three alloys Ti-35Pt-10Ir, Ti-22Pt-22Ir, and Ti-10Pt-32Ir (at%) close to the phase boundary but in the single phase of Ti(Pt, Ir) were prepared by the arc melting method. The shape memory effect and crystal structure were investigated by compression loading-unloading tests and high-temperature X-ray diffraction analysis, respectively. © 2012 Elsevier B.V.
  • Takahiro Mineta, Seiji Miura, Toshiji Mukai, Mikito Ueda, Tetsuo Mohri
    JOURNAL OF THE JAPAN INSTITUTE OF METALS AND MATERIALS 日本金属学会 ; 1937- 77 (10) 466 - 472 0021-4876 2013/10 [Refereed][Not invited]
     
    In Mg alloys, the most favorable deformation mechanism is the basal slip, and extension twinning also contributes to plastic deformation. Other mechanisms such as prismatic slips, pyramidal slips and twinning except for extension twinning scarcely occur. However, these slip systems also contribute to the plastic deformation of poly crystal Mg alloys, so the determination of CRSS of such non-basal slip systems are inevitable as a basis for the prediction of the deformation behavior of poly-crystal Mg alloys. Because of the difficulty of the evaluation of CRSS for non-basal slip by conventional compression test, newly designed "Pure shear test" is applied to evaluate the CRSS of the prismatic slip Mg alloy single crystals containing Y. Also a modification of Bridgman method using LiF + LiCl is attempted to obtain a pure-Mg single crystal.
  • Atsushi Hamaya, Toshiaki Horiuchi, Yuki Oohira, Satoshi Minamoto, Seiji Miura, Norihito Sakaguchi
    MATERIALS TRANSACTIONS 54 (5) 641 - 646 1345-9678 2013/05 [Refereed][Not invited]
     
    Three Mg-Zn-Y ternary alloys in the vicinity of X, Wand H phases were prepared and were isothermally heat treated at 833, 793, 723 and 673K to attain thermodynamic equilibrium. The microstructure was observed using electron probe microanalysis and transmission electron microscopy, and the chemical compositions of the equilibrium phases were analyzed using wavelength dispersive X-ray spectroscopy. The crystal structure of the Wand H phases were analyzed using X-ray diffraction, electron back scattering diffraction and electron diffraction pattern obtained by transmission electron microscopy. The Mg-Zn-Y ternary phase diagrams of the isothermal section were also calculated using the Thermo-Calc to compare with the experimental results. The X phase was found to be solidified in high-Mg alloys not in a manner of eutectic reaction as reported previously but in a manner of peritectic reaction. The W phase has a Heusler (L2(1)) type crystal structure with a stoichiometric composition of Mg1Zn2Y1, and fine mesh texture composed of alpha (Mg) and W phases was occasionally observed in non-equilibrium solidified parts, implying that the transient W phase has potential to be utilized as an additional strengthening phase. The equilibrium chemical composition of the H phase with a hexagonal crystal structure (P6(3)/mmc) was found to be different from that of the previous reports.
  • Kazuki Maruya, Ryoji Yamauchi, Takashi Narushima, Seiji Miura, Tetsu Yonezawa
    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 13 (4) 2999 - 3003 1533-4880 2013/04 [Refereed][Not invited]
     
    Many nanoporous metals have been applied for catalysis and show active properties. In this study, nanoporous platinum was successfully prepared from a Cu-Pt (50/50 w/w) alloy plate by electrochemical dealloying. In order to reveal their detailed structures in nanometer order, TEM observation of the surface area of the alloy plate was performed by using focused ion beam (FIB) for sample preparation. Peeling off the surface platinum nanoparticles could be also successfully preformed by using ultra sonification and their TEM observation revealed the units of the platinum nanoporous. structures.
  • Yoshimi Watanabe, Yan Bing Gao, Jun Qing Guo, Hisashi Sato, Seiji Miura, Hiromi Miura
    JAPANESE JOURNAL OF APPLIED PHYSICS 52 (1) 01AN04.1-01AN04.7  0021-4922 2013/01 [Refereed][Not invited]
     
    In this study, experiments were performed to clarify the grain-refining mechanisms of pure Mg cast by adding some grain refiners containing Al3Ti, TiC, TiB2, and AlB2 particles as heterogeneous nucleation sites. It is found that Al-5mass% Ti, Al-3mass% Ti-0.15mass% C, Al-5mass% Ti-0.2mass% B, and Al-5mass% Ti-1mass% B alloys are effective grain refiners for pure Mg, as well as for pure Al and Al alloys. The favourable heterogeneous nucleation sites in these refiners are considered to be TiC, TiB2, and AlB2 particles. (C) 2013 The Japan Society of Applied Physics
  • Yuting Wang, Seiji Miura, Akira Yoshinari
    Materials Research Society Symposium Proceedings 1516 109 - 114 0272-9172 2013 [Refereed][Not invited]
     
    Recently, Nb-Si based alloys have attracted considerable attention as potential candidate materials for ultra-high temperature applications, because of their low densities and high melting points. However, it is still very difficult to obtain materials with a good balance of high-temperature strength and room-temperature toughness. To address this issue, microstructure control is considered to be a promising method. In applying microstructure control to Nb-Si based alloys with a eutectic reaction (L → Nbss + Nb 3Si) and a eutectoid reaction (Nb3Si → Nb ss + Nb5Si3), the key is the control of Nb 3Si phase stability. Nb55(Nb solid solution) is considered as a ductile phase. In previous reports, it was revealed that different elements had different effects on the stability of Nb3Si. In particular, Mo and W (> 3 at %) destabilize the Nb3Si phase, while Ti and Ta stabilize it, and Zr acts as an accelerator for decomposition of Nb3Si. On the other hand, Cr is known to enhance the formation of the ductile Nb55 phase. In the present study, we investigated the effects of adding combinations of stabilizing, destabilizing, and accelerating elements with Cr, such as Cr and W, Cr and Ta, Cr and Zr. According to SEM observation, different microstructures were obtained with different combination of additives, and the fracture toughness at room temperature of these samples were also evaluated to reveal the effects of the microstructure on the mechanical properties of Nb-Si based alloys. © 2012 Materials Research Society.
  • Takuya Okawa, Seiji Miura, Tetsuo Mohri
    Materials Research Society Symposium Proceedings 1516 163 - 167 0272-9172 2013 [Refereed][Not invited]
     
    The development of a new high temperature structural material is recently required in various fields. As one of the potential materials, Nb-Si alloys have attracted attention due to their high melting point and low density. A microstructure composed of ductile Nb matrix containing finely dispersed spherical ND5Si3 phase is obtained by the addition of ternary elements such as Au and it is found that such microstructure is effective in improving room temperature toughness. The main purpose of the present study is evaluating fracture toughness of Nb-Si-Au alloys using small specimens and investigating the effects of the microstructure and other minor elements on the fracture toughness. Alloy ingots of Nb-15at.%Si-3at.%Au and Nb-3at.%Au are prepared by arc-melting under Ar atmosphere, followed by heat-treatments at up to 1500°C for 100 hours. Chevron notched specimens with a size of 1.0x2.0x 10mm are subjected to four-point bending tests under a laser confocal microscope for in-situ observation of crack propagation, and the effect of the microstructure and minor elements such as oxygen on the evaluated fracture toughness is investigated on both the Nb/Nb5Si3 alloys and the Nb solid solution (Nbss) alloys. ©2012 Materials Research Society.
  • DIRECT AND INDIRECT EFFECTS OF THE ALLOYING ELEMENTS ON THE MECHANICAL PROPERTIES OF NB-SI ALLOY
    MIURA Seiji
    An ECI (Engineering Conferences International) Conference proceedings 2013 [Not refereed][Not invited]
  • Yoko Yamabe-Mitarai, Toru Hara, Seiji Miura, Hideki Hosoda
    METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE 43A (8) 2901 - 2911 1073-5623 2012/08 [Refereed][Not invited]
     
    The martensitic transformation and shape memory effect of Ti-50(Pt, Ir)(50) with 5-37.5 at. pct Ir were investigated using differential thermal analysis (DTA), high-temperature X-ray diffraction (HT-XRD), and compression tests. The austenite finish temperature, A (f), increased with increasing Ir content from 1331 K (1058 A degrees C) in Ti-50 at. pct Pt to 1491 K (1218 A degrees C) in Ti-12.5Pt-37.5Ir. The structure of the parent and martensite phases was identified as B2 and B19 in all tested alloys. A large strain recovery rate was obtained in Ti-50(Pt, Ir)(50) with 10 to 30 at. pct Ir. The highest shape recovery ratio was 57 pct in Ti-25Pt-25Ir after deformation at 1123 K (850 A degrees C), followed by heating to above A (f). Using HT-XRD, the dependence of lattice parameter change on Ir content and temperature was investigated. The volume change during phase transformation from B2 to B19 was estimated using the lattice parameter of the B2 and B19 phases. Strain recovery is discussed along with volume change and lattice parameter change.
  • T. Horiuchi, H. Ikee, A. Hamaya, S. Minamoto, S. Nomoto, S. Miura
    THERMEC 2011, PTS 1-4 706-709 1170 - + 0255-5476 2012 [Not refereed][Invited]
     
    To elucidate the phase equilibria in the vicinity of the X or W phase in the Mg-Zn-Y ternary system, five Mg-Zn-Y ternary alloys containing the X or W phase were prepared and isothermally heat-treated to reach thermodynamic equilibrium. The microstructure and chemical compositions of the equilibrium phases of the alloys were analyzed. Furthermore, the crystal structure of the W phase was investigated, and the liquidus temperatures of the alloys were examined using differential thermal analysis. The results showed that the X phase can be crystallized not by a eutectic reaction, as reported previously, but by a peritectic reaction. They also showed that the W phase has the Heusler-type crystal structure with a stoichiometric composition of Mg1Zn2Y1, and that Mg and Zn in the W phase can be substituted for each other. The Mg-Zn-Y ternary phase diagram was calculated using an assessed CALPHAD thermodynamic database based on the experimental results of the present study, and compared with a recently reported phase diagram.
  • Effect of alloying elements on the shape of Nb silicide embedded in Nb matrix
    Seiji Miura, Toru Hatabata, Tetsuo Mohri
    “Non-linear Response of Conventional & Advanced Materials, and Multi-scale Modeling”, Proceedings of PLASTICITY ’12, Eighteenth International Symposium on Plasticity and its Current Applications 118 - 120 2012 [Refereed][Invited]
  • Effect of Al3Ti, TiC and TiB2 Particles on the Grain Refinement of Pure Magnesium
    Yoshimi Watanabe, Yan Bing Gao, Jun Qing Guo, Hisashi Sato, Seiji Miura, Hiromi Miura
    ISPlasma2012 182 - 182 2012 [Not refereed][Not invited]
  • Mechanical properties of Nb-Si based alloys with microstructure modified by applying phase stability concept
    Seiji Miura, Tatsuichi Tanahashi, Tetsuo Mohri
    Creep 2012/JIMIS 11, 12th International conference on Creep and Fracture of Engineering Materials and Structures, Proceedings D11  2012 [Refereed][Invited]
  • In situ crack observation of unidirectionally solidified Nb-Si based alloys
    T. Hatabata, S.Miura, T. Mohri
    Creep 2012/JIMIS 11, 12th International conference on Creep and Fracture of Engineering Materials and Structures, Proceedings D12  2012 [Refereed][Not invited]
  • Yulong Li, Chaoli Ma, Hu Zhang, Seiji Miura
    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 528 (18) 5772 - 5777 0921-5093 2011/07 [Refereed][Not invited]
     
    The room-temperature fracture toughness and high-temperature compression strength are investigated in directionally solidified Nb-Mo-Si-based alloys with aligned Nb-ss/Nb5Si3 lamellar structure. The fracture toughness is higher as grain size is reduced or annealing at 1300 degrees C for 100 h is applied. The normalized work of rupture (chi) in the in situ Nb-ss/Nb5Si3 lamellar structure is modeled and calculated to range from 0.10 to 0.38. Besides, the Nb-ss and Nb5Si3 are firmly connected on the fracture surface. Thus, the Nb-ss/Nb5Si3 interface is strongly bonded. Either reducing interface toughness or enhancing Nb-ss toughness is advantageous for interface decohesion. In the annealed Nb-17Si-10Mo-0.1Ga alloy, a small amount of Nb-ss/Nb5Si3 interface decohesion is observed because the annealing increases the toughness of Nbss. At 1250 degrees C and 1350 degrees C, the maximum compression strength is 620 MPa and 520 MPa, respectively. (C) 2011 Elsevier B.V. All rights reserved.
  • Yulong Li, Seiji Miura, Kenichi Ohsasa, Chaoli Ma, Hu Zhang
    INTERMETALLICS 19 (4) 460 - 469 0966-9795 2011/04 [Refereed][Not invited]
     
    Directional solidification in an optical floating zone furnace was employed to develop a fully-lamellar Nb-SS/Nb5Si3 structure for ingots having a composition of Nb-17Si-10Mo-3Al. It was determined that beta-Nb5Si3 is a faceted phase through the estimation of the entropy of melting and that the Nb-SS/beta-Nb5Si3 eutectic has a non-faceted/faceted structure, in which the microstructure is thought to be sensitive to growth conditions such as growth rate and rod-rotation speed. In the absence of the rotation speed of the seed rod, a fully-lamellar Nb-SS/beta-Nb5Si3 structure was obtained for growth rates below 10 mm/h. The relationship between lamellar spacing and growth rate was in agreement with the Jackson Hunt theory with lambda R-2 = 170 mu m(2) mm/h in this alloy. Electron backscatter diffraction analysis on both Nb-17Si-10Mo-3Al alloy and Nb-18Si-10Mo alloys revealed that the crystallographic orientation relationship in the as-grown Nb-SS/beta-Nb5Si3 lamellae was {112}(NbSS)//{100}(beta-Nb5Si3) and < 113 >(NbSS)//[001](beta-Nb5Si3). No preferred crystallographic orientation relationship was identified between either beta-Nb5Si3 or Nb-SS and alpha-Nb5Si3, but the Nb-SS/alpha-Nb5Si3 lamellar structure exhibited good stability at high temperature. It was inferred that one beta-Nb5Si3 may nucleate with several Nb-SS nucleation supposedly at the interface between the liquid and beta-Nb5Si3. (C) 2010 Elsevier Ltd. All rights reserved.
  • Seiji Miura, Yukiyoshi Tsutsumi, Tetsuo Mohri
    Materials Research Society Symposium Proceedings 1295 373 - 378 0272-9172 2011 [Refereed][Not invited]
     
    In order to understand the deformation and fracture behavior of Nb-Si alloys, in-situ observation was conducted during bending of small specimens at room and high temperatures. Nb-Si alloy ingots containing 18.1 at.%Si, 1.5 at.%Zr and 100 ppmMg were prepared by arc melting, followed by uni-axial solidification in an optical floating zone apparatus and a heat-treatment to obtain Nb/Nb5Si3 two-phase microstructure. Chevron-notched specimens with a dimension of 1x2x10mm were used for in-situ observation of bending tests under a confocal laser scanning microscope (CLSM) at room temperature and at 1140°C. At room temperature the Nb-Si alloy shows a fracture toughness of 8 MPa m1/2 and the crack propagation velocity seems to be not uniform, presumably due to the ductile Nb. At 1140°C the toughness of the alloy was about 20 MPa m1/2 and slower plastic deformation prior to the cracking was observed. The SEM observation of crack surfaces revealed that plastic deformation of Nb enhances the toughness of the alloy. © 2011 Materials Research Society.
  • Tatsuichi Tanahashi, Seiji Miura, Tetsuo Mohri
    Materials Research Society Symposium Proceedings 1295 207 - 212 0272-9172 2011 [Refereed][Not invited]
     
    Recently, Nb-Si alloys have attracted attentions as substitutional materials of Ni-based superalloys because of its low density and high melting point. For attaining good room temperature toughness of Nb-Si alloys, proposed is a microstructure-control technique by combining eutectic reaction (L-> Nb+Nb3Si) and eutectoid reaction (Nb3Si-> Nb+ Nb5Si3) for spheroidizing Nb5Si3 strengthening phase embedded in Nb matrix [1]. For the solid solution strengthening of Nb matrix phase W and Mo are very effective, but Nb 3Si phase disappears by adding these elements of as small as 3 at%. In contrast, Ti and Ta stabilize Nb3Si phase. For a further alloy development, establishment of an alloy design based on the control of phase stability of Nb3Si is needed. In the previous study [2], it was revealed that the phase stability of Nb3Si can be controlled by selecting appropriate Ta/Mo ratio. In the present study, this approach is expanded to other combinations of stabilizing and destabilizing elements of Nb3Si, such as Ti and W, Ta and W, and Ti and Mo. Vickers hardness tests were conducted on the heat-treated samples to reveal effects of additives on mechanical properties of Nb-Si alloy. © 2011 Materials Research Society.
  • Yoshiaki Kashiwaya, Tsuyoshi Nakamitsu, Hiroshi Kinoshita, Seiji Miura
    ISIJ INTERNATIONAL 51 (8) 1204 - 1212 0915-1559 2011 [Refereed][Not invited]
     
    It is widely known that the direct contact between solid carbon and iron oxide shows quite a fast reduction rate in comparison with CO gas reduction. However, it is difficult to sustain the physical contact between solid carbon and iron oxide. Furthermore, the contact mode will be different from the production method, which will affect the reaction kinetics strongly. In this study, different kinds of contacts between solid carbon and hematite were made to clarify the reaction mechanism. One contact mode is the deposition of the carbon layer on the hematite surface using a vacuum evaporation method. Another method is the implantation of carbon ions into hematite. Using XPS (X-ray photoelectron spectroscopy), the binding energy of Fe-O-C was measured. Heating under an argon atmosphere was carried out. Both samples showed quite different reaction behavior, though the temperature at the beginning of the reduction reaction was almost the same. From these results, it was determined that the position of carbon will change the reaction behavior drastically, because it is important how the CO gas escapes from the reaction site.
  • Y. Yamabe-Mitarai, T. Hara, S. Miura, H. Hosoda
    INTERMETALLICS 18 (12) 2275 - 2280 0966-9795 2010/12 [Refereed][Not invited]
     
    Martensitic transformation behavior and shape memory properties of Ti-50at%Pt were investigated using high-temperature X-ray diffractometry and loading-unloading compression tests. The structure of the parent and martensite phases was identified as 132 and B19, respectively. Changes in the lattice parameters of the martensite phase were investigated as a function of temperature. Applying the lattice parameter changes, the volume strain between 819 and B2 phases at 1473 K was estimated at 2.5%. The compression test was carried out at room temperature and at 1123 K. Strain was precisely measured using a strain gage for the test at room temperature and a CCD camera for the test at 1123 K. Strain recovery was observed during unloading at room temperature and at 1123 K, which was below the martensite temperature. Shape recovery was investigated for the samples tested at room temperature and at 1123 K by heating at 1523 K for 1 h. It was found that the strain recovery rate was 30-60% for the samples tested at room temperature and about 11% for the samples tested at 1123 K. (C) 2010 Elsevier Ltd. All rights reserved.
  • Yuichiro Yamamoto, Yoshiaki Kashiwaya, Seiji Miura, Masaru Nishimura, Kenji Katou, Seiji Nomura, Masahiro Kubota, Kazuya Kunitomo, Masaaki Naito
    TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN 96 (5) 104 - 112 0021-1575 2010/05 [Refereed][Not invited]
     
    The performance of coke in blast furnace (BF) used to prefer a high strength and low reactivity, generally, while the high reactivity coke commonly has a low strength. To overcome the contradiction, we are going to use the catalytic effect on the coke gasification. It is important to clarify the mechanism of coke gasification concerning to the coke microstructure and pore. In this study, the coke gasification was analyzed using mu-X-ray CT (Computed Tomography). The optimum conditions for the image processing of the data from the X-ray CT were obtained through the comparison with the cross section of the coke embedded in a resin. Nondestructive observation became possible. To improve resolution of the nondestructive observation, the sample shape was changed from spherical to cylindrical one and the observation conditions were adjusted to an optimum one. It was found that the resolution of the nondestructive observation of cylindrical sample was better than that of spherical sample. Using high precision mu-X-ray CT, the position of the catalyst added and the reaction behavior became clear. Furthermore, using new developed image processing of the data from the mu-X-ray CT, macroscopic reaction behavior of the catalyst became clear.
  • N. Sekido, S. Miura, Y. Yamabe-Mitarai, Y. Kimura, Y. Mishima
    INTERMETALLICS 18 (5) 841 - 845 0966-9795 2010/05 [Refereed][Not invited]
     
    Dislocation character and operative slip systems in alpha-Nb5Si3 were examined by transmission electron microscopy. Two-phase alloys comprised of (Nb) and alpha-Nb5Si3 were used in this study. Although few dislocations were present in the alpha-Nb5Si3 phase of a pre-deformed alloy, many developed after 15% of compressive deformation at 1673 K. Two types of the Burgers vectors were identified for alpha-Nb5Si3: <100] and 1/2 < 111]. The glide planes of dislocations were defined by the cross products between the Burgers vectors and the line vectors of the dislocations, by which the slip systems that operate in alpha-Nb5Si3 at 1673 K were determined as {011)<111], {100)<010], and {001)<100]. (C) 2009 Elsevier Ltd. All rights reserved.
  • Yuichiro Yamamoto, Yoshiaki Kashiwaya, Seiji Miura, Masaru Nishimura, Kenji Katou, Seiji Nomura, Masahiro Kubota, Kazuya Kunimoto, Masaaki Naito
    TETSU TO HAGANE-JOURNAL OF THE IRON AND STEEL INSTITUTE OF JAPAN 96 (5) 113 - 120 0021-1575 2010/05 [Refereed][Not invited]
     
    The performance of coke in blast furnace (BF) used to prefer a high strength and low reactivity, generally, while the high reactivity coke commonly has a low strength. To overcome the contradiction, it is important to develop a catalyst to increase the reactivity of carbon, so that the reaction mode can be changed from chemical reaction control to diffusion control. In this study, the reaction behavior of a ferro-coke was investigated, in which an iron oxide were added into a raw coal. Using high temperature laser microscope, in situ observation was carried out with the ferro-coke sample ground into tetragonal shape with 3.4 x 3.4 x 2.2 mm. Behavior of catalyst in coke was clarified through the in situ observations. It was found that the temperature at peak of reaction without catalyst was 1270 degrees C, while the coke with catalyst showed two peaks at 900 degrees C and 1270 degrees C. It was considered that redox reactions would exist in the system. The mechanism of redox reaction is shown as Eqs. (1), (2) and (3), mainly.FeO(melt) + C = Fe + CO (1)FeO(melt) + CO= Fe +CO2 (2)Fe + CO2 = FeO(melt) + CO (3)On the other hand, the coke gasification was analyzed using high precision mu-X-ray CT. The optimum conditions for the image processing of data from the mu-X-ray CT were obtained through the comparison with the cross section image of the coke embedded in the resin. Because of the smaller sample than the previous study, higher precision analysis was able to carry out.
  • T. Yamamoto, K. Fushimi, S. Miura, H. Konno
    OXIDE FILMS 25 (40) 3 - 15 1938-5862 2010 [Not refereed][Not invited]
     
    The influence of substrate dislocations on passivation behavior of a pure iron in pH 8.4 borate buffer solution was investigated. Cold rolling was employed to induce dislocation in the annealed substrate. The dislocation density on the cold rolled substrate depended on the reduction ratio (Red) and was maximum at Red = 60%. The electric charge consumed in the passivation and the passivity-maintaining current increased with increase in the dislocation density. EIS revealed that the dislocation exposed to the iron surface increased donor density in the passive film and reduced charge transfer resistance for the film aging. It was also demonstrated by rf-GDOES that a thick passive film formed on the cold rolled iron compared with that on annealed iron. These results suggest that substrate dislocations enhance the reactions at the substrate/film interface, resulting in the formation of the highly defective passive film.
  • Shigeharu Ukai, Akinobu Minami, Shigenari Hayashi, Norihito Sakaguchi, Seiji Miura
    PRICM 7, PTS 1-3 654-656 (Pt.1) 436 - 439 0255-5476 2010 [Refereed][Not invited]
     
    Nb, Al and Y(2)O(3) powders were mechanically alloyed together with 5 wt% stearic acid. The heavy plastic deformation of the powders by mechanical alloying led significant hardening to 970 Hv and the reduced grain size to 10 nm. Nb-Al base ODS alloys consolidated by HIP at 1500 degrees C and 150 MPa for 0.5 h gave the dual phase of Nb solid solution and Nb(3)Al compound. The oxide particles are of the hexagonal type YAlO(3) (YAH), with the size of 50 nm to 200 nm. The high-temperature ductility at 1200 degrees C and capability of the grain growth at 2000 degrees C were confirmed.
  • Seiji Miura, Tatsuichi Tanahashi, Yoshinao Mishima, Tetsuo Mohri
    PRICM 7, PTS 1-3 654-656 (Pt.1) 444 - + 0255-5476 2010 [Not refereed][Not invited]
     
    In order to spheroidize alpha-Nb5Si3 strengthening phase embedded in Nb matrix for attaining a good room temperature toughness of Nb-Si alloy, the authors have proposed a microstructure control technique by combining eutectic and eutectoid reactions. Nb3Si intermetallic compound formed during solidification is a key phase for the microstructure control, but its stability is very sensitive to the alloying elements. Nb3Si disappears by adding as small as 3 at% of W and Mo, while these elements are very effective for the solid solution strengthening of Nb phase. For a further alloy development, establishment of an alloy design concept based on the control of phase stability of Nb3Si is needed. Similarly to ferrous alloys such as stainless steels where Cr and Ni are added to control the stability of bcc phase and fcc phase, two alloying elements (one is a stabilizing element and the other is a destabilizing element for Nb3Si phase) are added to a Nb-Si binary master alloy and their microstructure is investigated using SEM. The stabilizing element Ta is found to enlarge the composition area where Nb3Si exists even with the destabilizing element Mo, and it is confirmed that the phase stability concept is useful for designing Nb-Si based alloys.
  • Itsuya Sato, Seiji Miura, Tetsuo Mohri
    PRICM 7, PTS 1-3 654-656 (Pt.1) 715 - 718 0255-5476 2010 [Refereed][Not invited]
     
    A commercial Mg alloy, AZ31B, has been used widely. In the texture of AZ31B sheet, each grain has its c-axis almost parallel to the sheet normal. Therefore, at the bending process of the sheet, basal slip system can not accommodate an in-plane plastic strain which is perpendicular to the c-axis of each grain. It is known that {10 (1) over bar2} twin can be formed by applying an extension strain parallel to the c-axis, which is equivalent to the a-axis compression strain. So in the bending deformation of the AZ31B sheet with a texture microstructure, it is expected that {10 (1) over bar2} twinning occurs. In this study, an in-situ bending test of AZ31B sheet with a texture was conducted under a confocal scanning laser microscope to observe twinning by applying compression stress along a direction almost perpendicular to the c-axis of grains. In addition, EBSD techniques were used for the analysis of crystal orientations. The process of twin development observed by the in-situ bending test can be summarized as follows; with the increase of the deformation strain, the total area of twins increases. However, it is noted that the growth of twins is apparent while the number of twins is almost constant during plastic bending deformmation. EBSD analysis suggested that twinning behavior obey Schmid's law even in the polycrystal.
  • Satoshi Minamoto, Sukeharu Nomoto, Atsushi Hamaya, Toshiaki Horiuchi, Seiji Miura
    ISIJ INTERNATIONAL 50 (12) 1914 - 1919 0915-1559 2010 [Refereed][Not invited]
     
    The Mg-Zn-Y alloys show a good mechanical strength which can be achieved with the precipitation hardening by intermediate phases (X Wand / phase) in Mg solid solution (a phase) However an accurate control of the microstructure formation is required in order to obtain good mechanical properties In this study experimental observations of microstructures of the Mg-Zn-Y system have been performed Then we have focused on developing CALPHAD (CALculation of PHAse Diagrams) thermodynamic database to obtain the Gibbs free energy to draw phase diagram of the system and to understand the precipitation behavior of the intermediate phases In order to understand the formation of microstructures we have performed simulations of solidification of the alloy with use of multi-phase-field method At the beginning the solidification process has been calculated for a large area then the zoomed in region of the lamellar structures of the a phase and the W phase have been analyzed Resulting optimum lamellar spacing reproduce experimental one well
  • Takatoshi Yamamoto, Koji Fushimi, Seiji Miura, Hidetaka Konno
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 157 (7) C231 - C237 0013-4651 2010 [Refereed][Not invited]
     
    The influence of substrate dislocations on the passivation behavior of pure iron in a pH 8.4 borate buffer solution was investigated. Cold-rolling was employed to induce dislocation in the annealed substrate. The dislocation density on the cold-rolled substrate depended on the reduction ratio (Red) and was maximum at Red = 60%. The electric charge consumed in the passivation and the passivity-maintaining current increased with an increase in the dislocation density. Electrochemical impedance spectroscopy revealed that the dislocation exposed to the iron surface increased the donor density in the passive film and reduced the charge-transfer resistance for the film aging. It was also demonstrated by radio frequency-glow discharge optical emission spectroscopy that a thick passive film formed on the cold-rolled iron compared with that on annealed iron. These results suggest that substrate dislocations enhance the reactions at the substrate/film interface, resulting in the formation of a highly defective passive film. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3425607] All rights reserved.
  • Kazufumi Sato, Satoshi Takizawa, Seiji Miura, Tetsuo Mohri
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 78 (11) 114003.1-114003.6  0031-9015 2009/11 [Refereed][Not invited]
     
    We perform kinetic Monte Carlo simulations of atomic diffusion in the Ti-Al system using activation energies calculated by embedded atom method (EAM). The activation energies strongly depend on the atomic species occupying the four atomic sites which locate nearest to the saddle point in the fee lattice. It is found, however, that the configuration of atoms on the other sites surrounding the jumping atom plays an essential role in the atomic ordering process: we fail to reproduce the formation of ordered nuclei in using the activation energies which depend only on the configuration of the nearest four atoms, and the system remains in disordered states even at very low temperatures. By introducing a correction term to the activation energies which takes into account the contribution of nearest neighbor atoms of the migrating atom, we can simulate growth of ordered embrios.
  • Seiji Miura, Yuki Murasato, Yoshihito Sekito, Yukiyoshi Tsutsumi, Kenji Ohkubo, Yoshisato Kimura, Yoshinao Mishima, Tetsuo Mohri
    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 510-11 317 - 321 0921-5093 2009/06 [Refereed][Not invited]
     
    Deformation behavior of Nb-Si-Zr alloys is investigated at various temperatures ranging from R.T. to 1670 K. The master alloy ingots composed of Nb-18.1 at% Si-1.5 at% Zr doped with Mg are Ar-arc-melted. The ingots contain Nb rods (radius: 1 mu m) in Nb(3)Si matrix formed by eutectic reaction. Alloys are subjected to heat treatments at 1923 K for 4-100 h to obtain a large Nb network structure with small silicide (alpha-Nb(5)Si(3)) particles by decomposing Nb(3)Si matrix into Nb and Nb(5)Si(3) through a eutectoid reaction. Compression tests are conducted at room temperature in air and at elevated temperatures in Ar atmosphere. At 1471 K the maximum strength is 500 MPa and compressive ductility is higher than 10% with a strain rate of 1.0 x 10(-4) s(-1), while at room temperature the maximum strength is over 1500 MPa and compressive ductility is about 1.5%. The high-temperature deformation obeys a power-law type equation. The stress exponent n is evaluated to be 4.8 and the apparent activation energy is 350kJ/mol. The Vickers indentation at room temperature revealed that the crack propagation at room temperature is suppressed effectively by ductile Nb. This suggests that the Nb aggregate in the network structure acts as a large Nb grain containing fine Nb(5)Si(3) particles, which might be beneficial for ductility at low temperatures. (C) 2009 Published by Elsevier B.V.
  • Nickel-Aluminides Long-Fiber Reinforced Nickel Matrix Composite fabricated by a Reaction at Narrow Holes Method
    Proceedings of 17th International Conference on Composite Materials (ICCM-17, Edinburgh) 1 - 10 2009 [Not refereed][Not invited]
  • N. Sekido, S. Miura, Y. Yamabe-Mitarai, Y. Kimura, Y. Mishima
    ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS 1128 413 - + 0272-9172 2009 [Not refereed][Not invited]
     
    Deformation behavior of (Nb)/alpha-Nb5Si3 two-phase alloys is examined by high temperature compression tests. The alloys exhibit brittle fracture behavior at temperatures up to 1473 K, while reasonable compressive deformability at 1673 K. Upon high temperature compression of the alloys, the flow stress gradually decreases after the peak stress due to the recrystallization/recovery in the (Nb) phase, as well as the increase in the density of mobile dislocations within the alpha-Nb5Si3 phase. Two types of slip systems that operate in alpha-Nb5Si3 have been identified as (011)<1<(1)over bar>1] and {001)<100] in the present study.
  • Kenichi Ohsasa, Seiji Miura
    ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS 1128 407 - 412 0272-9172 2009 [Refereed][Not invited]
     
    A numerical model was developed for the simulation of microstructure evolution during the solidification of Nb-Si eutectic alloy. In this model, the cellular automaton method was used to simulate the eutectic growth of Nb solid solution and Nb(3)Si intermetallics. Diffusion in liquid, mass conservation at the solid/liquid interface and local equilibrium at the solid/liquid interface with consideration of curvature undercooling were solved to determine the positions of the Nb/liquid and Nb(3)Si/liquid interfaces. In the alloy with eutectic composition of 17.5 at%Si, irregular eutectic growth morphology was observed in relatively low undercooling region. On the other hand, in high undercooling region over 50 K, dendrite morphology of Nb(3)Si was observed. In the simulation for the alloy with hypo-eutectic composition of 16.0 at%Si, Nb solid solution grew with cell morphology in low undercooling region, while coupled eutectic morphology was formed in higher undercooling region over 8 K. The growth velocity of the coupled growth increased with increase in the degree of undercooling. In the alloy with hypo-eutectic composition of 12.0 at%Si, cell and dendrite morphology of Nb was formed in whole undercooling region,
  • Yoshihito Sekito, Seiji Miura, Kenji Ohkubo, Tetsuo Mohri, Norihito Sakaguchi, Seiichi Watanabe, Yoshisato Kimura, Yoshinao Mishima
    ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS 1128 281 - + 0272-9172 2009 [Refereed][Not invited]
     
    In the present work Nb-18.1 Si-1.5Zr alloy rods are produced with a growth rate ranging from 1.5 to about 1500 mm/h using the optical floating zone (OFZ) furnace. A part of each specimen is heat-treated at 1650 degrees C for 100 h. The microstructure was observed using SEM and TEM and analyzed using EPMA and EBSD.Eutectic-cells are observed in as-grown specimens with a growth rate of 150 mm/h or higher. It is found by EBSD analysis that the solidification direction of Nb is along < 113 > and that of Nb3Si is along <001], and {112) of Nb and {110) of Nb3Si are parallel. The present crystallographic orientation relationship between Nb and Nb3Si is different from that found in previous reports by several researchers. It was also confirmed that the heat-treated microstructure in the specimen grown by OFZ with a growth rate of 150 mm/h is similar to that in the heat-treated specimen prepared by arc-melting.
  • Microstructure Control of E21 Fe3AlC-bcc Ferrite Dual Phase Alloy and Its Mechanical Properties
    Hiroaki Ishii, Megumi Kitamoto, Seiji Miura, Kenji Ohkubo, Tetsuo Mohri
    The Japan Society for Heat Treatment 49 (special issue 2) 514 - 517 2009 [Refereed][Not invited]
  • Yoshimi Watanabe, Hisashi Sato, Katsuya Mori, Su Min Lee, Ick Soo Kim, Hiromi Miura, Seiji Miura
    Advanced Composites for Efficiency and Environment - The US-Japan Conference on Composite Materials 2008, US-Japan 2008 (HTC-5)1-8  2008/12/01 [Not refereed][Not invited]
     
    Mg/SiC FGM is fabricated by the centrifugal method under different conditions. For this purpose, green compact of pure Mg chips and SiC particles was used as a master material. The microstructures and Vickers hardness of the successfully fabricated FGM were gradually changed depending on the region of the FGM samples. This tendency was more emphasized with increasing G number. This was caused by the distribution gradient of SiC and Mg2Si particles. Copyright ? 2008 by JSCM.
  • Toshiaki Horiuchi, Akemi Ono, Kentaro Yoshioka, Takero Watanabe, Kenji Ohkubo, Seiji Miura, Tetsuo Mohri, Shigeyuki Tamura
    MATERIALS TRANSACTIONS 49 (10) 2247 - 2253 1345-9678 2008/10 [Refereed][Not invited]
     
    Mg-Y-Zn alloys have attracted much attention in recent years due to their excellent mechanical properties, which are said to be the effect of the intermediate phase (X phase) in the Mg solid solution (alpha phase). The formation behavior of the X phase has been reported to be a eutectic type reaction in the Mg-Y-Zn pseudo-binary system. However, the phase diagram of this system still requires clarification. In the present Study, the 97.0Mg-1.3Zn-1.7Y (at%) alloy was prepared to clarify the liquidus and solidus in the liquid-solid coexistence region, and the solubility limit in the alpha phase. The chemical compositions of the alloy were analyzed by electron probe X-ray microanalysis after isothermal heat treatment. The results indicate that the Mg-Y-Zn ternary system can be represented as a pseudo-binary system between the alpha and X phases. In addition, the solidus line for the alpha phase has been clarified. The solubility limit for the alpha phase is not much different from that of the previous report, whereas the formation behavior of the X phase is not in the manner of a eutectic reaction, but rather that of a peritectic one. [doi: 10.2320/matertrans.MAW200822]
  • Hiroaki Kawamoto, Seiji Miura, Kaori Yano, Kenji Ohkubo, Tetsuo Mohri
    MATERIALS TRANSACTIONS 49 (5) 1107 - 1111 1345-9678 2008/05 [Refereed][Not invited]
     
    Improvement of deformability for Mg-based composite materials with a dispersion of Ti particles has been considered in terms of the Strain transfer through the interface, but is not fully understood during the deformation of ductile Ti particles. Mg-based composites composed of pure Mg and pure Ti plates was investigated to clarify the strain transfer through the Mg/Ti interface using crystallographic orientation analysis based on electron back-scattered diffraction (EBSD) patterns. It is suggested that the larger Schmid factor and lower residual strain energy (W) are significant for the operation of a prismatic slip system in the Ti grains.
  • Seiji Miura, Shigeki Imagawa, Takeshi Toyoda, Kenji Ohkubo, Tetsuo Mohri
    MATERIALS TRANSACTIONS 49 (5) 952 - 956 1345-9678 2008/05 [Refereed][Not invited]
     
    Effect of rare-earth elements (Y and Dy) on the mechanical properties of Mg solid solution single crystal is investigated. Comparing with the effect of other elements reported by previous studies, the solid solution strengthening by Y and Dy are much higher than that of other additives such as Zn for basal slip operation, while the isotropic strain by Zn atoms is higher than those of Y and Dy. Strain-rate changing tests were conducted for a further understanding of the dislocation motion and it revealed that the activation volumes estimated for Mg alloys with Y and Dy are much smaller than that of Zn-added alloy, while the activation enthalpy is almost the same. It was confirmed that the high strengthening effect by Dy addition is also found by Y addition, while the elastic interaction based on neither isotropic or anisotropic distortion are sufficient to explain the origin of the strengthening effect by Y and Dy addition.
  • T. Yamamoto, K. Fushimi, H. Habazaki, H. Konno, S. Miura
    ECS Transactions 16 (52) 133 - 140 1938-5862 2008 [Not refereed][Not invited]
     
    The effects of grain orientation and cold-rolling on the depassivation-repassivation behavior of polycrystalline irons were examined in pH8.4 borate buffer solution using in-situ micro-indentation technique. The depassivation rate on the passive iron surface during the downward drive of the indenter (penetration of an indenter tip into iron surface) depended on the grain orientation the highest rate was obtained on {100} surface, on which a possible main slip plane of {110} was normal to the surface. In contrast, the total electric charge required for repassivation during the downward and subsequent upward drives was not influenced by the grain orientation. The electric charge for repassivation was strongly influenced by the rolling reduction that changed the dislocation density at the specimen surface. There was a linear correlation between the electric charge normalized by residual dent area and the square root of the dislocation density. ©The Electrochemical Society.
  • Effect of Hardness on Depassivation-repassivation Behavior of Pure Iron in Borate Buffer Solution
    Proceedings of 214th ECS Meeting, PRiME 2008 1  2008 [Not refereed][Not invited]
  • DEFORMATION BEHAVIOR OF Nb-Si BASED ALLOY HAVING LARGE Nb GRAINS WITH Nb5Si3 DISPERSOIDS
    Plasticity 2008 proceeding(CD-ROM) 1107  2008 [Not refereed][Not invited]
  • Seiji Miura, Satoshi Takizawa, Kenji Ohkubo, Tetsuo Mohri
    JOURNAL OF THE JAPAN INSTITUTE OF METALS 日本金属学会 71 (10) 860 - 868 0021-4876 2007/10 [Refereed][Not invited]
     
    In order to search stable intermetallic compounds in a broad composition area in ternary, quaternary and higher-order systems, it is effective to utilize the calculation of formation enthalpy for screening prior to the experimental study. As the number of candidates is tremendously large for ternary and quaternary alloys, an augmented-spherical-wave (ASW) method was employed for fast calculation. To evaluate the accuracy of the calculation, the formation enthalpy of 132, L1(0) and B19 structures of 99 equi-atomic compounds are estimated, and the most stable structure for each alloy is compared with the literature. It is found that 75% of the reported structures are predicted by the calculation results, and B19 structure tends to be evaluated less stable than L1(0) structure. The formation enthalpy of Heusler-like structure with Co-Fe-Ti-Zr equi-atomic quaternary composition is also estimated and this quaternary compound is unstable comparing with the estimated formation enthalpy of binary B2-CoFe, CoZr, FeTi and FeZr. An experimental study revealed there is a phase near the composition of the quaternary compound, but the structure is Laves-C14 Fe2Zr, neither the Hensler type nor bcc-based structure. It is concluded that the combination of ASW calculation and the experimental study is suitable for a broad search of compounds with relatively symmetric structure.
  • Seiji Miura, Kenji Ohkubo, Tetsuo Mohri
    MATERIALS TRANSACTIONS 48 (9) 2403 - 2408 1345-9678 2007/09 [Refereed][Not invited]
     
    Mechanical properties of Ll(2)-Co-3(Al,W) polycrystalline sample are investigated by compression testing at various temperature ranging from room temperature to 1193 K. It was found that at room temperature the 0.2% flow stress is 410MPa and the compressive ductility is higher than 10%, whereas at 1193 K the 0.2% flow stress is 382 MPa and the compressive ductility is about 10%. Two candidates for the reaction scheme of the Co-rich region of the Co-Al-W ternary phase diagram are proposed by combining the results of microstructure observation, X-ray diffractometry and the previous report.
  • MIURA Seiji, OKA Kazuhiko, OHKUBO Kenji, MOHRI Tetsuo
    Journal of JSEM 日本実験力学会 7 (0) 78 - 82 1346-4930 2007/06 [Refereed][Not invited]
  • Seiji Miura, Kenji Ohkubo, Tetsuo Mohri
    INTERMETALLICS 15 (5-6) 783 - 790 0966-9795 2007/05 [Refereed][Not invited]
     
    Alloys based on Nb-silicides exhibit superior high temperature strength than the commercial nickel based superalloys. In order to improve the low-temperature ductility by microstructural control, authors have attempted to understand the nature of the eutectic and eutectoid reactions in Nb-rich portion of the Nb-Si binary system, especially the crystallographic orientation relationship among the phases using FESEM-EBSD. During the eutectic reaction it was found that Nb rods of about 1 mu m in diameter having a certain crystallographic orientation disperse in Nb3Si matrix in a eutectic cell. Then, during the following heat treatment Nb3Si decomposes into a lamellar structure composed of Nb and alpha-Nb5Si3 in a manner of eutectoid reaction. It is observed that eutectoid Nb plates tend to nucleate at the eutectic Nb rod because both of them have a similar crystallographic orientation, resulting in a network of Nb phase with fine alpha-Nb5Si3 dispersoids. The Nb network may act as a large Nb grain which is expected to show better mechanical properties at both low and high temperatures. Both the reaction kinetics of the eutectoid decomposition of Nb3Si and the tendency of the Nb network formation are significantly affected by doping elements, which are attributed to the control of the interfacial energies among phases. (c) 2006 Elsevier Ltd. All rights reserved.
  • S. Miura, H. Goldenstein, K. Ohkubo, H. Sato, Y. Watanabe, T. Mohri
    PRICM 6: SIXTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, PTS 1-3 561-565 439 - + 0255-5476 2007 [Not refereed][Not invited]
     
    Ni3Al-based alloys possess good oxidation resistance, moderate room and high temperature strength and ductility. Introduction of Cr-carbide particles through a solidification route is attempted to provide higher hardness and wear resistance. The mechanical and physical properties are measured at room temperature for several alloys with various carbon concentrations up to 2.0 wt.%. Hardness and wear resistance as well as compressive strength increase with increasing carbon concentration, while bend ductility decreases. Adhesion between carbides and matrix phase is good, and cracks propagate mainly through carbides. The crystallographic orientation relationships between constituent phases are also attempted using electron back-scattering diffraction (EBSD) technique. The thermal conductivity is found to be less sensitive to the alloy composition.
  • S. Miura, J. H. Kim, K. Ohkubo, Y. Kimura, N. Sekido, Y. Mishima, T. Mohri
    THERMEC 2006, PTS 1-5 539-543 1507 - + 0255-5476 2007 [Not refereed][Not invited]
     
    Various investigations have been attempted to improve the low temperature ductility of Nb-silicides by microstructural control while they show superior high temperature strength. Present authors have focused on the microstructure evolution through the eutectic and eutectoid reactions in Nb-rich portion of Nb-Si binary system, and with small amounts of additives (Zr or Mg) alloys large Nb grains with fine silicide (alpha-Nb5Si3) particles have been obtained, which is attractive for high temperature use. For further understanding of this phenomenon, the present study has two objectives; one is to apply the advanced solidification technique for further microstructure control, and the other is to investigate the effect of co-existence of Zr and trace amount of Mg on the microstructure evolution during the eutectoid reaction in terms of the interfacial energy between phases. EBSD analysis revealed that uni-directionally solidified alloy show the same crystallographic orientation relationship (O.R.) between Nb and alpha-Nb5Si3 with that in arc-melted alloy having the same composition. On the other hand, Mg-doped alloy containing Zr shows an O.R. which was not observed in previous works. This implies that Mg doping is effective to control the interfacial energy between Nb and alpha-Nb5Si3 even in Nb-Si-Zr alloys. Two-step heat-treatment is found to be effective to obtain finer microstructure, and a further investigation on the controlling factors of eutectoid decomposition will provide a proper route to well-controlled micro structures.
  • High-Temperature Shape Memory Effect of Ti-(Pt, Ir)
    Materials Science Forum 539-543 3273 - 3278 2007 [Not refereed][Not invited]
  • Mechanical properties of L12-Co3(Al, W) polycrystals at various temperatures
    S Miura, K Ohkubo, T Mohri
    Materials Transactions 48 2403 - 2408 2007 [Refereed][Not invited]
  • Seiji Miura, Kenji Ohkubo, Tetsuo Mohri, Takayuki Yoshioka, Toshio Narita
    ADVANCED INTERMETALLIC-BASED ALLOYS 980 487 - + 0272-9172 2007 [Refereed][Not invited]
     
    In order to attain a better oxidation resistance of Ni-based superalloys for high performance engines, a ReCr-based sigma-phase diffusion barrier coating between the MCrAlY bond coat (Al reservoir) layer and a Ni-based superalloy substrate has been proposed to suppress the diffusion of Al and other elements. The deformation behavior of TMS82+ superalloy specimens with coating layers composed of an Al-rich surface layer (corresponding to a bond coat) and a ReCr sigma-phase inner layer is investigated. In-situ observation of the bending tests using a Laser scanning confocal microscopy revealed that the crack formation in the Al-rich surface layer(s) on the tension side of the bend specimen occurs at an early stage of bending. On the other hand, small cracks in the a-phase layer under the Al-rich surface layer(s) are formed at the slip traces in the Ni-based superalloy single crystal substrate. This suggests a good adhesion between the a phase and the Ni-based superalloy. At the compression side, in both the Al-rich surface layer(s) and the sigma-phase layer no cracking was observed until the Al-rich surface layer(s) shows buckling,
  • Seiji Miura, Yuki Murasato, Kenji Ohkubo, Yoshisato Kimura, Nobuaki Sekido, Yoshinao Mishima, Tetsuo Mohri
    ADVANCED INTERMETALLIC-BASED ALLOYS 980 327 - + 0272-9172 2007 [Refereed][Not invited]
     
    In order to overcome the brittleness of Nb-Si intermetallic compounds, novel inicrostructure control through eutectic solidification and eutectoid decomposition reactions has been proposed for obtaining Nb matrix alloys with a Nb-silicide dispersion by the present authors. As the additions of Zr and Mg accelerate the eutectoid decomposition rate and spheroidization of Nb-silicide during heat treatment, the effects of these additives on the eutectic microstructure are investigated. The effect of the growth rate during the uni-directional solidification on the microstructure of a selected alloy was examined and it was found that the following eutectoid reaction rate is strongly affected by the growth rate.
  • Nobuaki Sekido, Yoshisato Kimura, Seiji Miura, Yoshinao Mishima
    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 444 (1-2) 51 - 57 0921-5093 2007/01 [Refereed][Not invited]
     
    Unidirectional solidification experiments were performed on the (Nb)/Nb3Si eutectic alloys in the Nb-Si binary and Nb-Ti-Si ternary systems. The effect of solidification rates on microstructure development was studied using an optical floating zone melting furnace within the solidification rates from 10 to 200 mm/h. For the binary invariant eutectic alloy, a planar eutectic microstructure forms at 10 mm/h, while cellular eutectic microstructures develop at the higher solidification rates. The orientation relationship between Nb and Nb3Si formed upon planar eutectic solidification is determined as: {110}(Nb)//{110)(Nb3Si), and < 112 >(Nb)//< 001](Nb3Si). For the ternary univariant eutectic alloys, the formation of cellular eutectic microstructures is prevailing for all over the rates of solidification. The growth of Nb3Si is faster than that of (Nb). The size distribution of (Nb) particles spreads widely in an asymmetric manner. The cell size variation against solidification rates is in a reasonable agreement with the theoretical prediction. (c) 2006 Elsevier B.V. All rights reserved.
  • MITSUI Kazuhiro, MIURA Seiji
    学際研究 (62) 2006 - 2013 1884-6955 2006/11/30 [Not refereed][Not invited]
  • Nobuaki Sekido, Yoshisato Kimura, Seiji Miura, Fu-Gao Wei, Yoshinao Mishima
    JOURNAL OF ALLOYS AND COMPOUNDS 425 (1-2) 223 - 229 0925-8388 2006/11 [Refereed][Not invited]
     
    The (Nb)/NTb3Si eutectic alloys in the Nb-Si binary and Nb-Ti-Si ternary systems were unidirectionally solidified in an optical floating zone melting furnace. The effect of solidification rates on microstructures of the alloys is investigated. The coupled growth of (Nb) and Nb3Si is observed in the binary alloy solidified at 10 mm/h. The ternary alloys exhibit the development of discontinuous (Nb) particles within the Nb3Si matrix. The unidirectionally solidified alloys show improved fracture toughness and enhanced high temperature compressive strength as compared with the arc-melted counterparts. The role of an aligned eutectic microstructure in toughening is discussed from the existing models based on the crack bridging and the crack deflection. (c) 2006 Elsevier B.V. All rights reserved.
  • Yoshihiro Terada, Kenji Ohkubo, Seiji Miura, Tetsuo Mohri
    PLATINUM METALS REVIEW 50 (2) 69 - 76 0032-1400 2006/04 [Refereed][Not invited]
     
    Thermal conductivity and thermal expansion were measured for the L1(2) intermetallic compounds Rh3X ( X = Ti, Zr, Hf, V, Nb, Ta) in the temperature range 300-1100 K to evaluate the feasibility of applying the compounds as ultra-high temperature structural materials. The thermal conductivities of Rh3X are widely distributed over the range 32-103 W m(-1) K-1 at 300 K, but the differences between the thermal conductivities diminish at higher temperatures. A trend is observed in that the thermal conductivity of Rh3X is greater if the constituent X belongs to Group 5 rather than to Group 4 in the Periodic Table. The coefficient of thermal expansion (CTE) values of Rh3X increase slightly with increasing temperature; values are concentrated around 10 x 10(-6) K-1 at 800 K. CTE values of Rh3X decrease as X appears lower in the Periodic Table. It is demonstrated that Rh3Nb and Rh3Ta are suitable for ultra-high temperature structural applications due to their higher thermal conductivities and smaller CTE values.
  • Yoshihiro Terada, Kenji Ohkubo, Seiji Miura, Tetsuo Mohri
    Platinum Metals Review 50 (2) 69 - 76 1471-0676 2006/04 [Refereed][Not invited]
     
    Thermal conductivity and thermal expansion were measured for the L1 2 intermetallic compounds Rh 3X (X = Ti, Zr, Hf, V, Nb, Ta) in the temperature range 300-1100 K to evaluate the feasibility of applying the compounds as ultra-high temperature structural materials. The thermal conductivities of Rh 3X are widely distributed over the range 32-103 W m -1 K -1 at 300 K, but the differences between the thermal conductivities diminish at higher temperatures. A trend is observed in that the thermal conductivity of Rh 3X is greater if the constituent X belongs to Group 5 rather than to Group 4 in the Periodic Table. The coefficient of thermal expansion (CTE) values of Rh 3X increase slightly with increasing temperature values are concentrated around 10 × 10 -6 K -1 at 800 K. CTE values of Rh 3X decrease as X appears lower in the Periodic Table. It is demonstrated that Rh 3Nb and Rh 3Ta are suitable for ultra-high temperature structural applications due to their higher thermal conductivities and smaller CTE values.
  • Yoko Yamabe-Mitarai, Toru Hara, Seiji Miura, Hideki Hosoda
    MATERIALS TRANSACTIONS 47 (3) 650 - 657 1345-9678 2006/03 [Refereed][Not invited]
     
    To develop high-temperature shape memory alloys, Ti-50(Pt,Ir)mol% compounds are noted because of their martensitic transformation from B2 to B19(2H) or 4H(40) structures above 1273 K. A thermal expansion measurement and loading-unloading compression test were performed for Ti-50(Pt,Ir) to determine if the shape memory effect or superelasticity was shown. The thermal expansion measurement indicated the shape recovery in some of the compounds. The maximum shape recovery was about 4% by reheating at the above martensite transformation temperature after a loading-unloading compression test. Superelasticity was also observed in ternary compounds. The potential of Ti-50(Pt,Ir) as a high-temperature shape memory alloy is discussed.
  • N Sekido, FG Wei, Y Kimura, S Miura, Y Mishima
    PHILOSOPHICAL MAGAZINE LETTERS 86 (2) 89 - 98 0950-0839 2006/02 [Refereed][Not invited]
     
    The crystallography of a Nb/Nb5Si3 lamellar microstructure formed by Nb3Si decomposition has been investigated by transmission election microscopy. Upon solidification of a Nb-10 at.% Ti-20 at.% Si alloy, the high-temperature phase Nb3Si is retained at room temperature. During annealing at 1673 K, the Nb3Si phase transforms into the Nb and Nb5Si3 (D8(1)) phases with a lamellar microstructure through a eutectoid reaction. The orientation relationship between Nb and Nb5Si3 is determined by selected-area diffraction analyses as (01(1) over bar) (Nb)//(12(3) over bar)(Nb5Si3), and [133](Nb)//[111](Nb5Si3). The present orientation relationship is explained by good atomic matching on the close-packed planes along the near close-packed directions.
  • S Miura
    JOURNAL OF PHASE EQUILIBRIA AND DIFFUSION 27 (1) 34 - 46 1547-7037 2006/02 [Refereed][Not invited]
     
    A unique method for describing and establishing the reaction scheme of a multicomponent phase diagram is proposed in terms of graph theory. A geometrical representation of the connections between invariant reactions is considered as the basis to introduce the matrix formula of a graph that models a reaction scheme; then the number of all possible reaction schemes is enumerated. With a matrix operation, the most probable (full or partial) reaction scheme(s) can be selected within available experimental data. A ternary phase diagram was chosen as an example to show how to relate with experimental data. It is also shown that the number of invariant reactions in a ternary phase diagram can be expressed as a function of the numbers of binary and ternary phases.
  • A Novel method for the Measurement of Thermal Expansion of Thin Film using Laser Scanning Confocal Microscopy
    Proceedings of International Symposium on Advanced Fluid/Solid Science and Technology in Experimental Mechanics 367 - 371 2006 [Not refereed][Not invited]
  • Microstructure control of Nb-Si based multi component alloys using Eutectic and Eutectoid reactions
    6 (2) 111 - 118 2006 [Not refereed][Not invited]
  • Geometrical approach to a reaction scheme of multi-component phase diagram and its application to a part of Al-Mo-Ti ternary phase diagram
    6 (2) 49 - 58 2006 [Not refereed][Not invited]
  • Mitarai(Yamabe) Y., Hara T., Miura S., Hosoda H.
    Proceedings of the 1992 Annual Meeting of JSME/MMD 一般社団法人 日本機械学会 2006 (0) 77 - 78 2006 [Not refereed][Not invited]
     
    To develop high temperature shape memory alloys, TiPt and TiIr are noted because of their possibility of phase transformation above 1273K. Then, the effects of Iridium (Ir) into TiPt on the constituent phases and the phase transformation temperature were investigated. It was found that the B19 phase appeared up to 37.5at% Ir in Ti (Pt, Ir) and the phase transformation temperature raised from 1303K in TiPt to 1473K in the Ti-12.5Pt-37.5Ir. Shape recovery and superelasticity of Ti-50 (Pt, Ir) were investigated by thermal expansion measurement in dilatometer and loading-unloading compression test. The shape recovery was found in all compounds in at least one of the testing methods. The highest shape recovery, about 4% was found in Ti-25Pt-25Ir using loading-unloading compression test. On the other hand, superelasticity was found in only ternary compounds. Larger superelasticity was observed in ternary compounds with higher Ir contents. Potential of Ti-50 (Pt, Ir) as high-temperature shape memory alloys is discussed.
  • S Miura, S Takizawa, T Suzuki, Y Mishima, T Mohri
    ACTA MATERIALIA 53 (19) 5175 - 5181 1359-6454 2005/11 [Refereed][Not invited]
     
    A theoretical approach to the hardening mechanism of L1(2)-Ni3Al compound with Al-rich off-stoichiometric composition is attempted based on the classical elastic interaction model between an edge dislocation and a unit cell with an equi-atomic composition embedded in Ni3Al. A tetragonal distortion is expected to arise from a local anisotropic atomic configuration in the unit cell which is recognized as a face-centered tetragonal-L1(0) or distorted B2 NiAl structure around an anti-site Al atom. According to the study by Cochardt et al. (Acta Metall 1955;3:533), it is found that the maximum point force F, on an edge dislocation from the local L1(0) unit cell increases with decreasing the cilai ratio of the L1(0) structure toward the stable B2 structure, which is expected from the authors' recent electronic structure calculations on the stability of L1(0)-NiAl relative to B2-NiAl. This increment of F-m by decreasing the cilai ratio accounts for a larger hardening in Al-rich Ni3Al than that in Ni-rich Ni3Al at 77 K. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
  • S Takizawa, S Miura, T Mohri
    INTERMETALLICS 13 (11) 1137 - 1140 0966-9795 2005/11 [Refereed][Not invited]
     
    For explaining asymmetry in the flow stress of Ni3Al alloy as a function of aluminum content, the structural energy of ordered NiAl alloy with the L1(0) structure is obtained with the electronic structure calculations based on the density functional theory. Quite a large distortion in the c-direction is found at the equilibrium, which means an L1(0)-like local structure appearing in the Al-rich region of the Ni3Al phase undergoes a large tetragonal strain. This tetragonal strain will give an explanation for the strengthening mechanism using the framework of Cochardt et al. The effect of the A1 concentration on the structural stability of L10 in terms of the DOS is also discussed to explain the concentration dependence of the B2-L1(0) martensitic transition temperature. (c) 2004 Elsevier Ltd. All rights reserved.
  • H Miura, Yang, X, T Sakai, H Nogawa, S Miura, Y Watanabe, JJ Jonas
    PHILOSOPHICAL MAGAZINE 85 (30) 3553 - 3565 1478-6435 2005/10 [Refereed][Not invited]
     
    The high temperature deformation behavior of Mg single crystals was precisely investigated using orientation imaging microscopy. For this purpose, Mg single crystals of various orientations were tensile tested in vacuum at temperatures between 473 and 673 K. A strain rate of 4.2 x 10(-4) s(-1) was employed. The elongations to fracture depended strongly on crystal orientation, the lowest fracture strains being associated with multiple slip. Single crystals in which single slip was activated exhibited extended ductilities corresponding to more than 1.5 in true strain. The strong orientation dependence of the ductility can also be correlated with the ease of occurrence of dynamic recrystallization (DRX), which took place in the multiple-slip specimens. The role of twinning in the initiation of DRX is also discussed.
  • MIURA SEIJI, OKA KAZUHIKO, OKUBO KENJI, MORI TETSUO
    実験力学 5 (3) 197 - 202 1346-4930 2005/09 [Refereed][Not invited]
  • MIURA SEIJI, OKUBO KENJI, MORI TETSUO, NARITA TOSHIO
    実験力学 5 (3) 203 - 208 1346-4930 2005/09 [Refereed][Not invited]
  • T Horiuchi, M Igarashi, F Abe, K Ohkubo, S Miura, T Mohri
    METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE 36A (8) 1999 - 2006 1073-5623 2005/08 [Refereed][Not invited]
     
    A phenomenological calculation of phase equilibria by combining the cluster variation method (CVM) with the Lennard-Jones-type (L-J-type) pairwise atomic interaction energies has been attempted for the Fe-Pd-Ni ternary system in order to examine the possibility of Ni as the substituting element for Pd. The calculated Ni content in an Fe-Pd-based L1(0) ordered phase at 863 K shows fairly good agreement with the experimental analysis performed for Fe-5Pd-5Ni alloy by energy-dispersive X-ray spectroscopy of a transmission electron microscope. The detailed calculation indicates that Ni is preferentially substituted in a Pd site in the L1(0)-ordered phase, which can be interpreted by the Lennard-Jones-type pairwise potentials employed for the present study. It is concluded from the thermodynamic point of view that Ni is a promising candidate as the substituting element for Pd in an Fe-Pd-based L1(0) ordered phase.
  • Y Yamabe-Mitarai, T Hara, S Miura, H Hosoda
    JOURNAL OF THE JAPAN INSTITUTE OF METALS 日本金属学会 69 (8) 634 - 642 0021-4876 2005/08 [Refereed][Not invited]
     
    It is known that some of platinum group metals base intermetallics have shape memory effect. We note PtTi because its phase transformation temperatures is at around 1273 K. The phase transformation of PtTi and the effect of Ir on the phase transformation were investigated by X-ray diffractometry (XRD), differential thermal analysis (DTA), in-situ surface observation in laser microscope, and microstructure observation in transmission electron microscopy (TEM). The shape recovery was investigated by dilatometry. Microstructure suggests martensitic phase transformation occurs in PtTi and (Pt, Ir) Ti. The shape recovery was found in some of the tested alloys. Potential of platinum group metals base intermetallics as high temperature shape memory alloys is discussed in this paper.
  • S Miura, K Ohkubo, Y Terada, Y Kimura, Y Mishima, Y Yamabe-Mitarai, H Harada, T Mohri
    JOURNAL OF ALLOYS AND COMPOUNDS 393 (1-2) 239 - 247 0925-8388 2005/05 [Refereed][Not invited]
     
    Isotherms of the Ir-rich portion of the Ir-Al-X (X: Ti, Zr, Hf) systems are presented. In all of the isotherms three-phase equilibrium is found and no ternary compound is observed. Solid solubility of each phase is confirmed by chemical analysis by wavelength dispersive X-ray spectroscopy (WDS). The direction of the solubility lobe of L1(2)-Ir3X with Al addition is explained in terms of the nearest neighbor interactions. Liquidus surfaces are also established by taking into account the microstructure of as-cast alloys, differential thermal analysis (DTA) data, Ir-X binary phase diagrams reported previously and the phase equilibria of the Ir-Al binary system investigated in the present study. (c) 2004 Elsevier B.V. All rights reserved.
  • Y Watanabe, R Sato, IS Kim, S Miura, H Miura
    MATERIALS TRANSACTIONS 46 (5) 944 - 949 1345-9678 2005/05 [Refereed][Not invited]
     
    Magnesium based functionally graded material (FGM) was fabricated by a centrifugal method from ZK60A (Mg-5.5 mass%Zn-0.6 mass%Zr) alloy. The applied G numbers are 40, 80 and 120, where the G number is the centrifugal force in unit of gravity. The specimen shape was cylindrical with 18 mm in length. Microstructures of the fabricated FGM specimens were observed using SEM. Energy dispersive X-ray analysis was performed to study the. chemical compositional gradients within the fabricated FGM specimens. It was found that concentration of Zr in the specimens increases toward the centrifugal force direction, while no or quite small chemical compositional gradient of MgZn2 appears. A hardness change along the centrifugal force direction was also found. The graded structures are caused by the difference in the formation mechanisms of compositional gradient during the centrifugal method between Zr and Zn.
  • S Miura, K Ohkubo, Y Terada, Y Kimura, Y Mishima, Y Yamabe-Mitarai, H Harada, T Mohri
    JOURNAL OF ALLOYS AND COMPOUNDS 395 (1-2) 263 - 271 0925-8388 2005/05 [Refereed][Not invited]
     
    Isotherms of the Ir-rich portion of the Ir-Al-X (X: V, Nb, Ta) systems composed of fcc-Ir solid solution ((Ir)(ss)), Ir-based L1(2) intermetallic compounds Ir3X and B2-IrAl are presented as a second report of a series of investigations on the phase equilibria in the (Ir or Rh)-Al-X (X: Ti. Zr and HE or. V. Nb and Ta) ternary systems. In both Ir-Al-Nb and Ir-Al-Ta systems fcc/L1(2)/B2 three-phase equilibrium is found. In Ir-Al-V system, Ir solid solution and Ir3V have close compositions each other and fcc/L1(2)/B2 three-phase equilibrium is expected. No ternary compound is observed in all of the isotherms. Solid solubility of each phase is confirmed by chemical analysis by wavelength dispersive X-ray spectroscopy (WDS). The direction of the solubility lobe of L1(2)-Ir3X with Al addition is explained in terms of the nearest neighbor interactions. Liquidus surfaces are also established by taking into account the microstructure of as-cast alloys, differential thermal analysis (DTA) data, and the Ir-Al and the Ir-X binary phase diagrams reported previously. © 2004 Elsevier B.V. All rights reserved.
  • 渡辺義見, 佐藤隆芳, KIM Isk‐Soo, 三浦誠司, 三浦博己
    傾斜機能材料論文集 2004 1 - 6 2005/03/31 [Not refereed][Not invited]
  • S Miura, M Aoki, Y Saeki, K Ohkubo, Y Mishima, T Mohri
    METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE 36A (3) 489 - 496 1073-5623 2005/03 [Refereed][Not invited]
     
    The effect of Zr on the formation of Nb/Nb5Si3 lamellar microstructure by eutectoid decomposition reaction of Nb3Si is investigated. It has been shown that the kinetics of the eutectoid decomposition of high-temperature Nb3Si phase into Nb and Nb5Si3 phases are sluggish in the binary Nb-Si system and that they are enhanced by Zr additions. The time-temperature-transformation (TTT) diagram for the decomposition is experimentally determined and the acceleration of the reaction by small Zr addition of 1.5 at. pct is confirmed by comparison with the reported TTT curves of binary and ternary alloys containing Ti. The role of the ternary element on the decomposition kinetics is discussed in terms of crystallographic orientation relationships (ORs) and Zr distribution in the parent Nb3Si phase during solidification.
  • 「高温レーザー顕微鏡を用いた金属材料高温変形直接観察の試み」
    エネルギー変換マテリアル研究センターシンポジウム、"2005 Symposium on Materials and Systems for Energy Conversion", CARECM 232 - 236 2005 [Not refereed][Not invited]
  • Orientation dependence of ductility of Mg single crystals at elevated temperature
    Materials Science Forum 193-196 488 - 489 2005 [Not refereed][Not invited]
  • Investigation on the microstructure and high temperature mechanical properties of Al3Ti-Mo3Al two-phase alloys
    Materials Science Forum 475-479 837 - 840 2005 [Not refereed][Not invited]
  • Effect of Temperature and Ternary Additives on the Crystallographic Orientation Relationships among Phases related to the Eutectoid Decomposition of Nb3Si
    MRS Symp. Proc. "Integrative and Interdisciplinary Aspects of Intermetallics" 842 279 - 285 2005 [Not refereed][Not invited]
  • 「ZK60A合金を用いて作製したマグネシウム基傾斜機能材料」
    2004年度傾斜機能材料論文集 1 (6) 2005 [Not refereed][Not invited]
  • Mechanical properties of (Pt, Ir)Ti
    Materials Science Forum 475-479 1987 - 1990 2005 [Not refereed][Not invited]
  • S Miura, H Okuno, K Ohkubo, T Mohri
    Integrative and Interdisciplinary Aspects of Intermetallics 842 455 - 460 0272-9172 2005 [Not refereed][Not invited]
     
    In-situ observation of the formation and disappearance of the surface relief associated with the twinning during the order-disorder transitions among CuAu-I (L1(0)), CuAu-II (PAP) and disordered fcc phases was conducted using Confocal Scanning Laser Microscopy equipped with a gold image furnace. The Retro effect was confirmed in poly-crystal samples, however no evidence was found in single-crystal samples. Also observed in poly-crystal samples are that the disordering temperature detected by the disappearing of relieves is different from grain to grain, and that grain boundary cracking alleviates the Retro effect. The observed phenomena were explained based on the crystallographic orientation relationship among grains investigated by FESEM/EBSD in terms of the elastic strain effect around grain boundaries induced by transition. It was confirmed that in each grain the surface relieves correspond to a set of two 10 111 planes having a < 100 > axis perpendicular to both planes in common. It was also found that the larger the average strain of two neighboring grains is, the lower the transition temperature. This observation was explained by the stress effect on the stability of a phase.
  • 三浦 誠司, 大久保 賢二, 毛利 哲雄
    実験力学 日本実験力学会 5 (3) 203 - 208 1346-4930 2005 [Refereed][Not invited]
  • 三浦 誠司, 岡 和彦, 大久保 賢二
    実験力学 日本実験力学会 5 (3) 197 - 202 1346-4930 2005 [Refereed][Not invited]
  • S Miura, H Shimamura, K Ohkubo, T Mohri
    PRICM 5: THE FIFTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, PTS 1-5 475-479 (Pt.1) 837 - 840 0255-5476 2005 [Not refereed][Not invited]
     
    Investigation on the crystallographic orientation relationships among D0(22)-Al3Ti, A15-Mo3Al and high temperature bcc phase consisting of an Al-Mo-Ti ternary alloy with an equi-axed two-phase structure was conducted by FESEM/EBSD analysis. The grains of intermetallic phases have certain crystallographic orientations each other, while the crystallographic orientation distributions become random after a high temperature deformation. This strongly suggests the grain boundary sliding and grain rotating govern the high temperature deformation, which is consistent with the fact that the strain-rate sensitivity m is 0.3 or higher during a steady-state compressive deformation.
  • H Miura, T Sakai, H Nogawa, Yang, X, Y Watanabe, S Miura
    MAGNESIUM - SCIENCE, TECHNOLOGY AND APPLICATIONS 488-489 193 - 196 0255-5476 2005 [Refereed][Not invited]
     
    Orientation-controlled Mg single crystals were tensile tested at temperatures between 473 K and 673 K at a strain rate of 4.2 x 10(-4) s(-1) in vacuum. Though all the single crystals showed high ductility compared with that of polycrystals, the ductility of the single crystals strongly depended on the crystal orientation. The [27 -1 -26 1] single crystal showed 0.57 fracture stra4 while the [3 8 -11 -1] single crystal showed superplastic behavior of ductility over 1.8 strain. The observed strong orientation dependence of ductility seemed to be caused by orientation dependence of ease occurrence of dynamic recrystallization (DRX) in the single crystals during high-temperature deformation. The orientation dependence of ductility of Mg single crystals will be discussed in detail concerning crystallographical orientations of the single crystals, occurrence of DRX and fracture.
  • S Miura, K Ohkubo, T Mohri
    Integrative and Interdisciplinary Aspects of Intermetallics 842 279 - 284 0272-9172 2005 [Refereed][Not invited]
     
    The authors have reported in the previous study that the sluggish decomposition of Nb3Si phase is effectively accelerated by Zr addition [1]. This is obvious at lower temperature range than the nose temperature of the TTT curve. In the present study a eutectic alloy containing 1.5 % of Zr was investigated. The crystallographic orientation relationships among phases, such as eutectic Nb and product phases formed by eutectoid decomposition of Nb3Si (eutectoid Nb and Nb5Si3 phases) in the Zr-containing sample which was heat treated at 1300 degrees C were investigated by FESEM/EBSD for. further understanding of the decomposition process in alloy with a different microstructure.
  • N Sekido, Y Kimura, S Miura, Y Mishima
    MATERIALS TRANSACTIONS 45 (12) 3264 - 3271 1345-9678 2004/12 [Refereed][Not invited]
     
    Design of two-phase alloys consisting of niobium solid solution (A2) and alpha-Nb5Si3 (D8(1)) phases in the Nb-Ti-Si tertiary system is pursued for ultra-high temperature structural applications. Compositional and annealing conditions are determined for the formation of A2/D8(1) lamellar microstructure via cutectoid decomposition of Nb3Si (tP32) phase in the Nb-Si binary and Nb-Ti-Si tertiary system. Addition of titanium is found to result in increased room temperature toughness, but decreased high temperature strength. Enhancement of mechanical properties is achieved by applying the directional solidification technique. Mechanical properties of the alloys are discussed from microstructural point of view.
  • JH Kaneko, N Susa, S Tsuchida, M Watanabe, S Miura, T Mizuno, Y Yamauchi, M Hashiba, T Oku, A Homma, F Fujita, T Ino, M Furusaka, T Sawamura, HM Shimizu, Y Kiyanagi
    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 529 (1-3) 307 - 309 0168-9002 2004/08 [Refereed][Not invited]
     
    A thin GSO scintillator was developed aiming at applications for the neutron science. In order to fabricate a large and thin GSO scintillator in the future, fabrication was started from two types of GSO powders. Although several GSO films were fabricated by evaporation techniques, these films did not have luminescence in photo luminescence (PL) spectroscopy. Thus, these samples were annealed up to 1550degreesC. However, it resulted in no luminescence observation. In response to these results, GSO powders were directly annealed; a phenomenon looking like melting and sintering were observed for Gd2Si2O7:Ce at a temperature higher than 1500degreesC. This sample was quasi-transparent and had luminescence at 405 nm in PL spectrum. In addition, this sample was tougher than a GSO single crystal. In conclusion, the prospect of fabrication of a thin GSO scintillator by combination of annealing and mechanical polishing was obtained. (C) 2004 Elsevier B.V. All rights reserved.
  • S Miura, H Shimamura, J Fujinaka, T Mohri
    INTERMETALLICS 12 (7-9) 771 - 777 0966-9795 2004/07 [Refereed][Not invited]
     
    The high temperature deformation behavior of two-phase intermetallic-based alloys composed of the DO22-Al3Ti and A15-Mo3Al phases is investigated. It is found that the equi-axed two-phase structure formed by an isothermal heat treatment is very stable even after a high-temperature heat treatment and, moreover, the microstructure is retained even after heavy deformation at high temperature. The strain-rate sensitivity m is 0.3 or higher, and a steady state deformation is attained. Compressive deformability is found to be extremely high with the equi-axed two-phase structure. Conversely, a lamellar structure was found to be unstable during deformation. The strain-rate sensitivity m of the specimens with a lamellar structure is almost the same as that of the equi-axed two-phase structure, and the resulting microstructure strongly suggests that the deformation is concentrated at the boundaries between the lamellar colonies, where the equi-axed two-phase structure is formed during deformation by spheroidization. (C) 2004 Elsevier Ltd. All rights reserved.
  • Ryuho Sato, Yoshimi Watanabe, Seiji Miura, Hiromi Miura
    Keikinzoku/Journal of Japan Institute of Light Metals 軽金属学会 54 (11) 522 - 526 0451-5994 2004 [Refereed][Not invited]
     
    Three kinds of magnesium based titanium particles-dispersed functionally graded materials (FGMs) were fabricated by a centrifugal solid-particle method. Materials were pure magnesium, AZ91D ( 9.23Al-0.7Zn-0.028Si-0.23Mn-0.0019Fe 0.0014Cu 0.001Ni-0.0009Be-bal.Mg) and Mg-6mass%Zn alloys. The specimen shape was cylinder with 15 20mm in length. Microstructures of FGM specimens were observed using an optical microscopy (OM) or a scanning electron microscopy (SEM). 2 vol%Ti was added into Mg 6 mass%Zn by a vortex addition technique in order to fabricate Mg-6 mass%Zn-2 vol%Ti master alloy. It was found that a large number of titanium particles were observed in the outer region of the cylinder, since the titanium particles migrate to outer region during the centrifugal solid-particle method. In this way, the magnesium based titanium particles dispersed FGM can be successfully fabricated by the centrifugal solid-particle method. Moreover, Vickers hardness increases with increasing the amount of titanium particles.
  • H Ishii, K Ohkubo, S Miura, T Mohri
    MATERIALS TRANSACTIONS Japan Institute of Metals 44 (9) 1679 - 1681 1345-9678 2003/09 [Not refereed][Not invited]
     
    E2(1)-Fe3AlC carbide (kappa) in the Fe-Al-C ternary system is known to have ductility at room temperature. It forms a lamellar structure similar to the pearlite with a ferrite (alpha) phase through a eutectoid-like reaction from an austenite (gamma) phase and improved mechanical properties are expected by replacing cementite to kappa phase. The mechanical properties of alpha + kappa two-phase lamellar structure were investigated through micro-Vickers hardness measurements and compression tests at room temperature in order to compare with those of pearlite steels. A typical mean inter-lamellar spacing of Fe-8 at%Mn-13 at%Al-7 at%C alloy aged at 773 K for 100 h was 60 nm and its yield stress and micro-Vickers hardness were 1880 MPa and 580 HV, respectively. Yield stress and micro-Vickers hardness of these specimens were higher than those of pearlite steels regardless of the mean inter-lamellar spacing. Those results seem to be rationalized by taking the solid solution hardening of ferrite phase into account.
  • H Ishii, K Ohkubo, S Miura, T Mohri
    MATERIALS TRANSACTIONS 44 (9) 1679 - 1681 1345-9678 2003/09 [Refereed][Not invited]
     
    E2(1)-Fe3AlC carbide (kappa) in the Fe-Al-C ternary system is known to have ductility at room temperature. It forms a lamellar structure similar to the pearlite with a ferrite (alpha) phase through a eutectoid-like reaction from an austenite (gamma) phase and improved mechanical properties are expected by replacing cementite to kappa phase. The mechanical properties of alpha + kappa two-phase lamellar structure were investigated through micro-Vickers hardness measurements and compression tests at room temperature in order to compare with those of pearlite steels. A typical mean inter-lamellar spacing of Fe-8 at%Mn-13 at%Al-7 at%C alloy aged at 773 K for 100 h was 60 nm and its yield stress and micro-Vickers hardness were 1880 MPa and 580 HV, respectively. Yield stress and micro-Vickers hardness of these specimens were higher than those of pearlite steels regardless of the mean inter-lamellar spacing. Those results seem to be rationalized by taking the solid solution hardening of ferrite phase into account.
  • R Nino, J Fujinaka, H Shimamura, S Miura, T Mohri
    INTERMETALLICS 11 (6) 611 - 623 0966-9795 2003/06 [Refereed][Not invited]
     
    Phase equilibria in Ti-lean part of the Al-Mo-Ti ternary system is investigated to understand the microstructure evolution of near-equi-atomic MoAl alloys containing Ti up to 17 at.%. A partial reaction scheme is proposed based on experimental study. A high temperature ternary A2(bcc)-beta phase with Ti concentrations ranging from 13 to 17 at.% decomposes into A15 Mo3Al-D0(22) Al3Ti two-phase lamellar structure in a manner similar with a eutectoid reaction through a continuous cooling. The decomposition kinetics of the high temperature A2 phase is suppressed by adding Ti. Fine equi-axed two-phase structure is also obtained by an isothermal aging of a retained high temperature A2 phase. (C) 2003 Elsevier Science Ltd. All rights reserved.
  • S Miura, T Mohri
    JOURNAL OF UNIVERSITY OF SCIENCE AND TECHNOLOGY BEIJING 10 (3) 47 - 50 1005-8850 2003/06 [Not refereed][Not invited]
     
    A part of Al-Ti-Mo-Cr quaternary phase diagram is constructed for the microstructure control of D0(22)-Al3Ti or its derivative, L1(2)-(Al,Cr)(3)Ti, -based alloys. It was found that quaternary bee phase equilibrates with either D0(22)-Al3Ti or L1(2)-(Al,Cr)(3)Ti, or both, exist in large compositional areas. The mechanical properties is strongly affected by precipitates appearing, and presumably alloy microstructures.
  • Y Terada, K Ohkubo, S Miura, JM Sanchez, T Mohri
    MATERIALS CHEMISTRY AND PHYSICS 80 (2) 385 - 390 0254-0584 2003/05 [Refereed][Not invited]
     
    Thermal conductivity and thermal expansion for Ir3X (X = Ti, Zr, Hf, V, Nb, Ta) were measured in the temperature range between 300 and 1100 K. The thermal conductivities of Ir3X are distributed in the range from 41 to 99 W m(-1) K-1 at 300 K, while the difference of thermal conductivities becomes less emphasized at higher temperatures. The coefficients of thermal expansion (CTEs) of Ir3X are insensitive to temperature, which fall around 8 x 10(-6) K-1 at 800 K. (C) 2002 Elsevier Science B.V. All rights reserved.
  • Y Terada, K Ohkubo, S Miura, JM Sanchez, T Mohri
    JOURNAL OF ALLOYS AND COMPOUNDS 354 (1-2) 202 - 207 0925-8388 2003/05 [Refereed][Not invited]
     
    Thermal conductivity and thermal expansion were measured for the L1(2) intermetallic compounds Rh3X (X=Ti, Zr, Hf, V, Nb, Ta) in the temperature range between 300 and 1100 K to evaluate the feasibility of applying the compounds to high temperature structural materials. The thermal conductivities of Rh3X are widely distributed in the range from 32 to 103 W m(-1) K-1 at 300 K, while the difference of the thermal conductivities becomes less emphasized at higher temperatures. A trend is observed that the thermal conductivity of Rh3X is larger when the constituent X belongs to group 5 rather than 4 in the periodic table. The coefficients of thermal expansion (CTE) of Rh3X slightly increase with increasing temperature, and they are concentrated around 10 X 10(-6) K-1 at 800 K. A trend is that the CTE of Rh3X is reduced as the position of X goes downward in the periodic table. It is demonstrated that Rh3Nb and Rh3Ta are suitable for high temperature structural applications due to the larger thermal conductivities and the smaller CTE. (C) 2003 Elsevier Science B.V. All rights reserved.
  • H Ishii, S Miura, T Mohri
    DEFECT PROPERTIES AND RELATED PHENOMENA IN INTERMETALLIC ALLOYS 753 351 - 356 0272-9172 2003 [Not refereed][Not invited]
     
    The structure of E2(1) is a derivative of L1(2) structure with an interstitial carbon in the body center or the octahedral interstitial site. In the Fe-Al-C ternary system E2(1)-Fe3AlC intermetallic is known to precipitate in gamma-austenite alloys. For the high temperature application, the stability of microstructure is a key issue and the control of the lattice misfit is essential. By adding some elements to Fe-Al-C alloys, the lattice constant can be controlled, and enhancement of the stability of gamma-austenite + E2(1)-Fe3AlC two phase structure is expected. In this study, phase stability and lattice parameter of E2(1) phase in the (Fe-Mn)-(Al-M)-C system (M=Si, Ge) are investigated. In both systems, no significant changes in microstructures were observed within the composition range of concern. The lattice constant of E2(1)-Fe3AlC phase, however, does not show decrease with the addition of Si or Ge. This result is different from what was expected. By WDS analysis, it was revealed that Si tends to distribute mainly in gamma phase, and Ge concentrates in E2(1)-Fe3AlC phase. It was found that the lattice constants of E2(1) phases are very close to those of L1(2) structure estimated from the atomic radii of constituent elements which are evaluated from those in binary alloys and compounds. The distribution behavior of Si and Ge can be related to tolerance factor which strongly affects the stability of phases.
  • Thermal properties of IrAl-B2 compound with Ni, Co and Fe
    Proc. for Symp. on ADVANCED RESEARCH OF ENERGY TECHNOLOGY 2003, CARET 299 - 307 2003 [Not refereed][Not invited]
  • S Miura, S Takizawa, Y Mishima, T Mohri
    DEFECT PROPERTIES AND RELATED PHENOMENA IN INTERMETALLIC ALLOYS 753 33 - 38 0272-9172 2003 [Not refereed][Not invited]
     
    One of the unsettled issues of the mechanical properties of Ll(2)-Ni3Al compound is the effect of off-stoichiometry on the 0.2% flow stress at low temperature region. 0.2% flow stress at 77 K increases as deviating from the stoichiometric composition to both Ni-rich and Al-rich sides, but in Al-rich side the increasing rate is higher. According to the XRD results for the binary Ni3Al alloys, however, the composition dependence of the lattice constant is the same in both sides of the stoichiometric composition, which implies that the magnitude of lattice strain induced at off-stoichiometric composition is symmetrical. And it is not rational to associate the strengthening mechanism to a sole effect of isotropic strain due to an atomic size difference. In this study, attempts are made to explain the additional strengthening in M-rich alloys in terms of the tetragonal distortion hardening mechanism, which arises from anisotropic atomic configuration around an anti-site Al atom.
  • S Miura, H Unno, T Yamazaki, S Takizawa, T Mohri
    JOURNAL OF PHASE EQUILIBRIA 22 (4) 457 - 462 1054-9714 2001/08 [Refereed][Not invited]
     
    The present work reports the results of a reinvestigation of the gamma liquidus and solidus temperatures of the Ni-Al system and the gamma /Ni5Zr eutectic reaction temperatures in the Ni-Al-Zr system. In the Ni-Al binary system, it is found that the stability of the Ni-rich gamma solid solution phase is enhanced by small additions of Al with the melting temperature of the gamma phase and that the melting temperature reaches a congruent maximum at a few at.% Al. The temperature of the eutectic reaction L --> gamma + Ni5Zr in the Ni-Zr binary edge is confirmed to be 1196 degreesC by differential thermal analysis (DTA), rather higher than the value reported previously. The reaction temperature increases with Al addition to reach or exceed 1206 degreesC, forming a "saddle point," then decreasing to reach 1187 degreesC or below by flowing into a ternary invariant reaction. These findings can be explained by gamma /liquid equilibrium in the Ni-Al binary system.
  • S Miura, YM Hong, T Suzuki, Y Mishima
    JOURNAL OF PHASE EQUILIBRIA 22 (3) 345 - 351 1054-9714 2001/06 [Refereed][Not invited]
     
    A systematic investigation was carried out to determine both liquidus and solidus surfaces of the Ni-solid solution (gamma) in the Ni-Al-X ternary phase diagrams successively by differential thermal analysis (DTA) technique. Each of the Group V elements of the periodic table, V, Nb, and Ta, was chosen as a ternary additive X in the present study. The gamma -solvus was also taken into account in determining a temperature range for a solid solution treatment above the gamma -solvus, i.e., "the window," as well as the maximum solubility limit of gamma -Ni solid solution.
  • R Nino, S Miura, T Mohri
    INTERMETALLICS 9 (2) 113 - 118 0966-9795 2001/02 [Refereed][Not invited]
     
    The behavior of cracking in Mo Al intermetallics with two different interlamellar spacings is investigated by micro Vickers tests at room temperature. The experimental results show the coarse lamellar structure can suppress crack nucleation even under a high load of 9.8 N, whereas the fine one starts being cracked under a low load of 2.94 N. It contradicts to the general observation that toughness of alloys is better with finer grains. The experimental observations are discussed in terms of a fracture mechanics model including dislocation emission at the crack tip. The present model shows that stress concentration at crack tip tends to increase with decreasing interlamellar spacing. The experimental results are qualitatively explained by the present model. (C) 2001 Elsevier Science Ltd. All rights reserved.
  • S Miura, T Mohri
    PRICM 4: FORTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, VOLS I AND II 1947 - 1950 2001 [Not refereed][Not invited]
     
    Microstructural design of Mg-based alloys is proposed. Ductile particles are added (introduced by solidification route) to be dispersed at the brittle grain boundaries in order to alleviate high stress concentration caused by a limited number of slip systems that can operate in hcp Mg alloys during plastic deformation. Based on a broad search of Mg-X binary phase diagrams, Ti is chosen as a ductile dispersoid because it equilibrates with Mg. As the proof stress of Ti is much higher than that of pure Mg, the matrix phase should have enough strength to deform Ti particles simultaneously. Several high-strength Mg alloys are selected as a matrix, and it was shown experimentally that the dispersion of Ti is effective to improve bending ductility of the composites.
  • Control of Microstructure by Heat Treatment to Overcome the Trade-Off Balancing in the Niobium Silicide Based MMC as Ultra-High Temperature Smart Materials
    Trans. Mat. Res. Soc. Japan 26 145 - 148 2001 [Not refereed][Not invited]
  • Effect of E21-Fe3AlC Precipitation on Mechanical Properties of Gamma-Austenite Stabilized by Addition of Mn and Co
    MRS Symp. Proc., ”High-Temperature Ordered Intermetallic Alloys IX" 646 N5.20.1-N.5.20.6  2001 [Not refereed][Not invited]
  • Microstructural Evolution and Mechanical Properties of Al3Ti-based Multi-Phase Alloys
    MRS Symp. Proc., "High-Temperature Ordered Intermetallic Alloys IX" 646 N5.15.1-N.5.15.6  2001 [Not refereed][Not invited]
  • Microstructural control of Al3Ti-based alloys designed by multi-component phase diagrams
    Seiji Miura, Juri Fujinaka, Tetsuo Mohri
    Processing and Fabrication of Advanced Materials X 287 - 300 2001 
    In the Al-Mo-Ti ternary system, a bcc-phase field extends from the Ti-Mo edge to high-Al region at high temperatures, and at low temperature the low Ti region is replaced partially by a two-phase region composed of an A15-Mo3Al and a D022-Al3Ti phases. It enables us to form a fine lamellar structure. Besides, most of the Ll2-trialuminides stabilizing elements also act as the bcc-βTi phase stabilizer. So, the designing of the bcc-Ll2 two-phase alloys also can be expected by adding them to the Al-Mo-Ti alloys. In order to apply such ideas for microstructural control, a series of studies on the phase relations in the Al-Mo-Ti-X quaternary systems have been carried out to introduce an Ll2-(Al,X)3Ti phase and/or bcc phase for ductile-phase toughening. It is found that, by additions of X = Cr, an Ll2-(Al,Cr)3Ti phase appears near the two-phase region composed of the D022-Al3Ti and bcc phases. By heat treatments, the D022-Al3Ti and/or Ll2-(Al,Cr)3Ti phases precipitates from the bcc phase, and no voids are observed. The mechanical properties of these alloys are also investigated by Vickers indentation tests.
  • Effect of E21-Fe3AlC precipitation on mechanical properties of γ -austenite stabilized by addition of Mn and Co
    Seiji Miura, Hiroaki Ishii, Tetsuo Mohri
    Materials Research Society Symposium - Proceedings 646 N5201 - N5206 0272-9172 2001 
    Effects of Co addition on the phase relation and mechanical properties of an E21-Fe3AlC phase in the Fe-Mn-Al-C system are investigated. The relation between the γ-austenite and E21 phases is the same with Co-free alloys. Two kinds of precipitation processes of E21 phase from γ-austenite matrix are observed: a fine E21 phase precipitation and a cellular structure formation from grain boundaries. The cellular structure formation is explained in relation to the lattice mismatch evaluated by XRD. The lattice mismatch is estimated to be ∼3%, rather higher than that of γ/γ' in Ni-based superalloys, and the volume fraction of the E21-Fe3AlC phase precipitated in the γ-austenite phase is as large as 30%. The micro-vickers hardness increases with increasing Al or C, caused by the increase in the volume fraction of the E21-Fe3AlC phase.
  • N Sekido, Y Kimura, FG Wei, S Miura, Y Mishima
    JOURNAL OF THE JAPAN INSTITUTE OF METALS 日本金属学会 64 (11) 1056 - 1061 0021-4876 2000/11 [Refereed][Not invited]
     
    Effects of lamellar spacing on the mechanical properties of (Nb)/(Nb, Ti)(5)Si-3 two-phase alloys with a fine lamellar structure have been investigated for an improvement in room-temperature toughness and high-temperature strength. Lamellar spacing of the ahoy are controlled, without changing the volume fraction and composition of each phase, by varying annealing temperature for the decomposition of high-temperature phase (Nb, Ti)(3)Si into (Nb) and (Nb, Ti)(5)Si-3. A Time-Temperature-Transformation diagram (TTT diagram) was determined for a Nb-25 mol%Si-10 mol%Ti ahoy. It was found that the decomposition of (Nb, Ti)(3)Si in the Nb-Si-Ti system is kinetically faster than that of Nb3Si in the binary Nb-Si system. Average lamellar spacing, lambda, of the alloy is characterized by the degree of super-cooling, DeltaT, following a relationship as "lambda proportional to1/DeltaT". Coarse lamellar structure shows better room temperature compressive plastic strain before fracture and higher elevated temperature strength. The alloys investigated in this study show superior compressive strength at over 1000 degreesC as compared with some commercial Ni-based superalloys.
  • CL Ma, Y Tan, H Tanaka, A Kasama, R Tanaka, S Miura, Y Mishima, S Hanada
    MATERIALS TRANSACTIONS JIM 41 (10) 1329 - 1336 0916-1821 2000/10 [Refereed][Not invited]
     
    Microstructures and phase equilibria in cast and annealed Nb-Mo-Si alloys near the Nb-Mo binary were studied using X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and electron beam microprobe analysis (EPMA). A broad range of Nb and Mo compositions were investigated for Si compositions ui, to 30 mol%. Microstructural and microchemical evidence provide a clear definition of the Nh-Mo-Si liquidus surface projection and an isothermal section diagram at 1973 K.
  • Y Kimura, M Takahashi, H Hosoda, S Miura, Y Mishima
    INTERMETALLICS 8 (7) 749 - 757 0966-9795 2000/07 [Refereed][Not invited]
     
    Mechanical behavior of multi-phase alloys, consisting of intermetallic compounds B2 type CoAl and E2(1) type Co3AlC with primary solid solution (Co), was investigated by compression tests over a wide temperature range from 77 to 1273 K. It has been revealed that E2(1) Co3AlC is a good candidate of coexisting phase with B2 CoAl to improve the alloy's ambient temperature ductility and its elevated temperature strength. Most of the multi-phase Co-Al-C ternary alloys exhibit fairly good compressive ductility at whole test temperatures, even at 77 K. All the alloys show the anomalous positive temperature dependence of strength at intermediate temperatures. The deformation mechanism of E2(1) Co3AlC is expected to be the same as that of L1(2) intermetallic compounds because of the close resemblance of their crystal structures. The three-phase B2/E2(1)/(Co) alloy, 70Co20Al10C(at%), exhibits excellent ductility of virtually unlimited ambient temperature compressive plastic strain and the highest strength around 340 MPa at 1273 K. (C) 2000 Elsevier Science Ltd. All rights reserved.
  • S Miura, K Honma, Y Terada, JM Sanchez, T Mohri
    INTERMETALLICS 8 (7) 785 - 791 0966-9795 2000/07 [Refereed][Not invited]
     
    A preliminary study of the mechanical properties of Rh-based L1(2) intermetallic compounds Rh3Ti, Rh3Nb and Rh3Ta is carried out by micro-vickers hardness tests at room temperature and compression tests at various temperatures ranging from room temperature to 1673 K. A cold-rolling test is also conducted on a Rh3Ti plate. Although high temperature ductility-loss is observed in all compounds, Rh3Ti shows good ductility at all temperatures investigated. Both Rh3Nb and Rh3Ta show a weak positive temperature dependence of strength (stress anomaly) at around 1273 K which is about half the melting point for both intermetallic compounds. The stress anomaly is discussed in terms of a phase stability concept based on the Kear-Wilsdorf (K-W) mechanism. High work hardening rates of Rh3Nb and Rh3Ta, which cause high vickers hardness at room temperature, are also attributed to the K-W mechanism. (C) 2000 Elsevier Science Ltd. All rights reserved.
  • T Shoji, S Miura, T Mohri
    MATERIALS TRANSACTIONS JIM 41 (5) 585 - 588 0916-1821 2000/05 [Refereed][Not invited]
     
    In order to take multiple behavior of both mobile and immobile dislocations into account, Reaction-Diffusion equation is employed and a stress-strain curve is calculated. Characteristic three stages of a stress-strain curve are reproduced. The serration observed in the early stage of the deformation is interpreted based on the microscopic inhomogeneous multiplication process of dislocations leading to self-organization.
  • S Miura, Y Terada, T Suzuki, CT Liu, Y Mishima
    INTERMETALLICS 8 (2) 151 - 155 0966-9795 2000/02 [Refereed][Not invited]
     
    Thermal conductivity of 3Ni-1Al elemental powder compacts was measured using a laser-flash method as a function of temperature, compact density and heat treatment. Temperature dependence of thermal conductivity of the compacts is similar to that of pure Ni and Al metals. Heat treatment has a significant effect on the thermal conductivity of the compacts as particles are joined together to form Ni solid solution and intermetallic phases on powder surfaces. Fast diffusion on powder surfaces during heat treatment results in the formation of intermetallic phase zones in the interior of the former Ni particles. (C) 2000 Elsevier Science Ltd. All rights reserved.
  • S Miura, Y Mishima, T Suzuki
    DEFORMATION, PROCESSING, AND PROPERTIES OF STRUCTURAL MATERIALS 255 - 266 2000 [Not refereed][Not invited]
     
    Systematic investigations on both poly- and single crystalline Ni,AI have shown the existence of singularity of creep behavior at stoichiometry as well as the stress anomaly of the octahedral slip at intermediate temperatures and the athermal stress of the cube slip. We revealed that a viscous motion of dislocations on {111} plane governs the creep deformation of Ni,AI at a temperature range higher than the peak temperature, and that the mechanism governing the stress anomaly persisted its effect on the dislocation motion even at such high temperatures. There are large number of studies attempting to give an explanation for the stress anomaly with a basis of the cross-slip model proposed by Kear and Wilsdorf. Then the cross-slipped parts can be expected to move with a dragging mechanism with a diffusion mechanism at the high temperature range. The double-kink type locking parts are composed of a pair of jogs, one of which acts as a vacancy source and the other acts as a vacancy sink. For the climb motion of both of jogs, vacancy migration is required from ones to the others. A simple model including Kear-Wilsdorf type locking mechanism is attempted to unify the singularity in both creep behavior and stress anomaly in terms of a jog-drag motion of dislocation on {111} slip plane. By taking the effect of Al concentration on inter-diffusion coefficient of Ni3Al, both the singularity at stoichiometry and the effect of the deviation from the stoichiometry on creep behavior could be explained semi-quantitatively, and a path to an extended model for the effect of solid-solution on the creep behavior will be also shown in the presentation.
  • S Miura, S Yamamoto, K Ohkubo, T Mohri
    MAGNESIUM ALLOYS 2000 350-3 183 - 188 0255-5476 2000 [Not refereed][Not invited]
     
    Temperature dependence of the deformation behavior of Mg-alloy single crystals containing 0.5 at.%Dy or Zn is investigated by compression tests at various test temperatures ranging from 77 K to 473 K. The basal slip operates and the CRSS increases with decreasing temperature at the temperature range lower than room temperature. The CRSS of Mg-Dy alloy is higher than that of Mg-Zn alloy at all the test temperatures. The activation volume and the activation energy are estimated by the strain-rate changing test. The activation volume evaluated for each alloys is almost the same, 1000-4000 b(3), and the activation energy of the Mg-Dy alloy is rather higher than that of the Mg-Zn alloy. Measurement of lattice constants of Mg-Dy polycrystals reveals that both the lattice constants of a-axis and c-axis increase linearly with increasing Dy concentration, whereas c/a ratio decreases and it deviates from the ideal value of c/a (1.633) for hcp lattice.
  • H Hosoda, T Sugimoto, K Ohkubo, S Miura, T Mohri, S Miyazaki
    INTERNATIONAL JOURNAL OF APPLIED ELECTROMAGNETICS AND MECHANICS 12 (1-2) 9 - 17 1383-5416 2000 [Refereed][Not invited]
     
    Martensitic and magnetic transformation temperatures were investigated for Ni2MnGa alloys as a function of the degree of long-range order (LRO) associated with L2(1) structure. The de ree of order was changed by changing the heat treatment temperature. Besides, thermal properties such as thermal expansion (CTE), specific heat (C-p) and thermal conductivity (A) were measured up to 1273 K. It was found that with increasing the heat treatment temperature, the degree of second neighbor ordering lowered, but that the degree of first neighbor ordering did not show good correlations with the heat treatment temperatures. Martensitic transformation temperature (M-s) and Curie temperature (T-c) vary with the square of the degree of LRO. C-p and lambda at room temperature are 29.5 Jmol(-1)K(-1) and 23.2 Wm(-1)K(-1). CTE is ranged between 15 x 10(-6)K(-1) and 34 x 10(-6)K(-1). Temperature dependence of these thermal properties is described.
  • Gruneisen Parameters in Intermetallic Compounds NiAl and Ni3Al
    Proceedings of the 1998 International Symp. on Advanced Energy Technology, Part C: Advanced Microscopy and Its Application to Materials Science 118 - 123 2000 [Not refereed][Not invited]
  • Geometrical Approach to Multicomponent Phase Diagrams
    Proceedings for Symp. on Advanced Research of Energy Technology 2000 435 - 442 2000 [Not refereed][Not invited]
  • Y Ohta, S Miura, Y Mishima
    INTERMETALLICS 7 (11) 1203 - 1210 0966-9795 1999/11 [Refereed][Not invited]
     
    Development of a sintering process to fabricate iron disilicides with a line grain structure is pursued using elemental powders as starting materials with additions of Al. The Al additions are expected to involve liquid Al-rich phase during sintering to accelerate the reaction kinetics. At the same time, additions are made of Co and Cu, the former being an n-type dopant while the latter might promote metal-to-semiconductor transition upon annealing after sintering. The effects of such additions on the sintering kinetics, constituent phases in the products, and their thermoelectric properties are examined. It is shown that fabrication of sintered iron disilicides using elemental powders, heretofore believed to be difficult, becomes possible with Al additions. Then a mechanism of sintering in the Fe-Si-Al ternary system is proposed, and finally a series of demonstrations is given for the changes in thermoelectric properties depending upon the doping element used. It becomes evident that the thermoelectric figure of merit of the present materials is equivalent to that of the conventionally fabricated iron disilicides. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.
  • R Nino, S Miura, T Mohri
    MATERIALS TRANSACTIONS JIM 40 (9) 935 - 937 0916-1821 1999/09 [Refereed][Not invited]
     
    Formation and evolution processes of microstructure of Mo-Al alloys retarded by addition of 10 at%Ti are studied through various heat treatments. Fine acicular Mo,AL precipitates are observed inside a grain for a specimen quenched at 1673 K as an initial stage of the eutectoid decomposition of bcc phase. II suggests that there is a crystallographic orientation relationship between the bce matrix and A15 precipitates. By changing heat treatment conditions, fraction of fine lamellar structure decreases and spheroidized area increases. Subsequent aging treatment at lower temperature also provides the spheroidized structure. A coarse equiaxed structure is observed for a specimen quenched at 1673 K then aged at 1173 K.
  • T Shoji, M Ohno, S Miura, T Mohri
    MATERIALS TRANSACTIONS JIM 40 (9) 875 - 878 0916-1821 1999/09 [Refereed][Not invited]
     
    By employing stress-strain constitutive relationships within Gilman-Johnston and Alexander-Haasen models, transient behavior of calculated stress-strain curves is examined in the light of Cottrell-Stokes law. It is pointed out that the incorporation of the interaction force between mobile and immobile dislocations are indispensable to satisfy Cottrell-Stokes law.
  • S Miura, YM Hong, T Suzuki, Y Mishima
    JOURNAL OF PHASE EQUILIBRIA 20 (3) 193 - 198 1054-9714 1999/06 [Refereed][Not invited]
     
    A systematic investigation has been tarried out to determine both the gamma liquidus and solidus surfaces above the Ni solid solution in the Ni-AI-X ternary phase diagrams successively by differential thermal analysis. Each of the group IV elements in the periodic table, Ti, Zr, and Hf, was chosen as the ternary additive X in the present study. As a basis, gamma liquidus and solidus temperatures in the Ni-Al binary system were reinvestigated and evaluated. The gamma solvus was also taken into account to determine a temperature range for a solid-solution treatment above the gamma solvus, generally called "the window;" as well as the maximum solubility limit of gamma Ni solid solution.
  • S Ueno, T Fukui, R Tanaka, S Miura, Y Mishima
    MATERIALS TRANSACTIONS JIM 40 (5) 369 - 372 0916-1821 1999/05 [Refereed][Not invited]
     
    Role of ternary solute element Nb on the C40 --> C11b phase transformation of the MoSi2 phase in MoSi2/Mo5Si3 eutectic alloys which occurs during heat treatment is discussed in this paper. In the case of stoichiometric MoSi2, a mixture of C40 and C11b phases can be prepared by low-pressure plasma spraying method, in which phase transformation from the metastable C40 to stable C11b is recognized during heating at around 800 degrees C. It is found that the MoSi2, phase in an as-cast eutecric MoSi2/Mo5Si3 alloy with 8.5 at%Nb consist only of metastable C40 phase. The transformation from C40 to C11b in this alloy does not occur by heating up to 1200 degrees C but a portion transforms into C11b by heating at 1400 degrees C. It is shown that the Nb concentration in C40 phase is higher than that in C11b phase in this alloy, which must be relevant to the observed transformation behavior.
  • T Fukui, S Ueno, R Tanaka, S Miura, Y Mishima
    JOURNAL OF THE JAPAN INSTITUTE OF METALS 63 (5) 613 - 616 0021-4876 1999/05 [Refereed][Not invited]
     
    Effects of Nb or V additions on microstructure and hardness of MoSi2/Mo5Si3 eutectic alloys are investigated for the improvement of room temperature toughness of multi-phase intermetallic alloys based on MoSi2. Alloys prepared by the argon are melting process have compositions of 4-23 mol%Nb or 10-19 mol%V which substitutes Mo in MoSi2 and Mo5Si3 phases. Examinations are made on microstructural observation by back scattered electron image, X-ray diffraction for phase identification, the concentration of Nb or V in the constituent phases by EPMA, and Vickers hardness of the multi-phase alloys in both macro- and microscopic scales. The phase constitution changes from the two-phase, MoSi2(C11b) and (Mo, Nb)(3)Si-5, to the three-phase, MoSi2(C11b)/(Mo, Nb)Si-2 (C40)/(Mo, Nb)(5)Si-3, With increasing Nb additions. In the series of alloys with V additions, a similar shift from the two- to the three-phase is accompanied with increasing V addition. Macroscopic hardness of the multi-phase alloys with Nb addition exhibits a complex concentration dependence, in which with increasing Nb content, the hardness first decreases, exhibits a minimum and then increases back. The reason could be attributed to the fact that the hardnesses of the C40 and Glib phase have individual dependence on Nb concentration as revealed by micro-scale hardness measurement. For the improvement in toughness, Nb additions to the eutectic alloys may be preferred because the MoSi2/Mo5Si3 eutectic microstructure is fine as compared with that obtained by the V addition.
  • TENSILE AND CREEP RUPTURE PROPERTIES OF Co + Co3AlC0.5 TWO PHASE ALLOYS
    MRS Symp. Proc., "High-Temperature Ordered Intermetallic Alloys VIII 552 KK5.32.1-KK5.32.6  1999 [Not refereed][Not invited]
  • EFFECT OF ADDITIVES ON EUTECTOID REACTION AND MECHANICAL PROPERTIES OF Nb-Nb5Si3 ALLOYS
    High-Temperature Ordered Intermetallic Alloys VIII, MRS Symp.Proc. 552 KK6.9.1-KK6.9.5  1999 [Not refereed][Not invited]
  • Formation of Microstructures in Mo-Al alloys and Its Mechanical Properties
    Proceedings of PTM''99 197 - 201 1999 [Not refereed][Not invited]
  • The phase transformation from C40 to C11b in Nb added MoSi2-Mo5Si3 system
    Toshihiko Fukui, Shunkichi Ueno, Ryohei Tanaka, Seiji Miura, Yoshinao Mishima
    MATERIALS TRANSACTIONS 40 369 - 372 1999 [Refereed][Not invited]
  • Effect of additives on eutectoid reaction and mechanical properties of NbNb5Si3 alloys
    Seiji Miura, Yasuhiko Saeki, Tetsuo Mohri
    Materials Research Society Symposium - Proceedings 552 KK6.9.5  0272-9172 1999
  • R Nino, S Miura, T Mohri
    JAPAN INSTITUTE OF METALS, PROCEEDINGS, VOL 12, (JIMIC-3), PTS 1 AND 2 197 - 200 1999 [Refereed][Not invited]
     
    Formation and evolution processes of microstructure of Mo-Al alloys are investigated through various heat treatments. A fine lamellar structure is observed for a specimen quenched at 1773K and it spheroidizes by subsequent aging treatment at low temperature. A coarse lamellar structure grown from a primary Mo3Al phase is also observed. Micro Vickers hardness shows little dependence on microstructure. The size, not morphology, of microstructure plays primary role for the suppression of crack initiation and propagation.
  • S. Ueno, T. Fukui, R. Tanaka, S. Miura, Y. Mishima
    Materials Transactions 日本金属学会 40 (5) 369 - 372 1345-9678 1998/05/01 [Refereed][Not invited]
  • Mechanical Properties of Co-Base Alloys Strengthened by E21-Type Intermetallic Compound Co3AlC
    The Third Pacific Rim International Conf. on Advanced Materials and Processing (PRICM 3) 2355 - 2360 1998 [Not refereed][Not invited]
  • Microstructure and Ductility of Multi-Phase Intermetallic Alloys in the Nb-Si-Ti System
    The Third Pacific Rim International Conf. on Advanced Materials and Processing (PRICM 3) 2393 - 2398 1998 [Not refereed][Not invited]
  • Mechanical Properties of Mo-Al Alloys with Lamelar Structure
    The Third Pacific Rim International Conf. on Advanced Materials and Processing (PRICM 3) 2317 - 2322 1998 [Not refereed][Not invited]
  • ZL Peng, S Miura, Y Mishima
    MATERIALS TRANSACTIONS JIM 38 (7) 653 - 655 0916-1821 1997/07 [Refereed][Not invited]
     
    High temperature creep behavior of a nickel-rich Ni-3(AI, Ta) with the Ll(2), structure is investigated in order to clarify the influence of crystallographic orientation. The single crystals with four different orientations are deformed in compressive creep at the temperatures ranging from 1123 to 1273 K under a constant load with initial shear stresses being from 35 to 120 MPa for the (111)[(1) over bar 01] slip system. The results show a distinct orientation dependence of creep strength, although shape of creep curves, stress exponent and the activation energy seem to be independent on orientation. It is shown, however, that the internal stress measured by strain transient dip tests is found to be orientation-dependent and that the creep behavior is independent on orientation if these are analyzed with the effective stress instead of the applied shear stress.
  • JY Park, MH Oh, DM Wee, S Miura, Y Mishima
    SCRIPTA MATERIALIA 36 (7) 795 - 800 1359-6462 1997/04 [Refereed][Not invited]
  • Y Ohta, S Miura, Y Mishima
    PROCEEDINGS ICT'97 - XVI INTERNATIONAL CONFERENCE ON THERMOELECTRICS 295 - 298 1997 [Not refereed][Not invited]
     
    Sintering process to fabricate iron disilicides with a fine grain structure is pursued using elemental powders as starting materials. Additions of Al to the binary Fe-Si system are attempted. This is because Al has a considerably lower melting point than Fe and Si and hence liquid Al phase would be involved upon sintering to help accelerating the reaction kinetics to form iron disilicides. Sintering of ternary iron disilicides is attempted also with additions of Co and Cu, the former being an n-type dopant while the latter might promote metal-to-semiconductor transition upon annealing after sintering. Effects of such additions are examined on the sintering kinetics, constituent phases in the products, and their thermoelectric properties. It is shown that fabrication of sintered iron disilicides using elemental powders becomes possible with Al additions, for which a mechanism of sintering in the Fe-Si-Al ternary system is proposed. Also a series of demonstration is given for the changes in thermoelectric properties with difference in doping element.
  • S Miura, ZL Peng, Y Mishima
    HIGH-TEMPERATURE ORDERED INTERMETALLIC ALLOYS VII 460 431 - 436 0886-7860 1997 [Not refereed][Not invited]
     
    High temperature creep behavior of a nickel-rich Ni-3(Al,Ta) with the L1(2) structure is investigated in order to clarify the influence of crystallographic orientation with respect to the stress axis. The single crystals with four different orientations are deformed in compressive creep at temperatures ranging from 1123 to 1273 K under a constant load, initial shear stress being 35 to 120 MPa for (1 1 1)[(1) over bar 0 1] slip system. The results show a distinct orientation dependence of creep strength, although shape of creep curves, stress exponent and the activation energy seem to be independent of the orientation. It is shown, however, the internal stress, being measured by strain transient dip tests, is found to be orientation dependent and the creep behavior is independent on orientation if it is interpreted using the effective stress instead of the applied shear stress.
  • S Miura, T Ohashi, Y Mishima
    INTERMETALLICS 5 (1) 45 - 59 0966-9795 1997 [Refereed][Not invited]
     
    Intermetallic phases and the liquid phase are estimated using thermodynamic calculations as a function of temperature, the amount of phases and diluents, and Ni concentration in liquid Al during the reaction synthesis for Ni-Al binary alloys having arbitrary compositions under an adiabatic condition. Calculations use available thermodynamic data concerning intermetallic compounds and the liquid phase. Reaction synthesis experiments are then performed on compactions of powder mixtures which have several binary compositions. The effect of some fundamental conditions which relate to the conditions for calculation are investigated and the results obtained are discussed in terms of the amount of liquid phase estimated. It is found that the calculated amount of liquid phase in Ni-Al elementary powder compacts during the synthesis reaction are in good agreement with the experimental results; however, other factors are needed to understand the densification behavior of specimens with diluents such as liquid migration and formation of a skeleton structure. (C) 1996 Elsevier Science Limited.
  • Y Mishima, M Kato, Y Kimura, H Hosoda, S Miura
    INTERMETALLICS 4 S171 - S179 0966-9795 1996 [Refereed][Not invited]
     
    A summary is presented of the recent advances in the development of multiphase intermetallic alloys towards improved room temperature ductility investigated by the present authors. The alloy systems of interest are Ni-Al-Be, Co-Al-Ni-Ti, and Co-Al-C, in which two- or three-phase alloys can be designed involving the L1(2), B2 and the primary solid solution, hereby denoted as (Ni) or (Co,Ni) in the first two systems, while the B2, E2(1), and the primary solid solutions, denoted as (Co) in the latter system. It is shown that by choosing a proper combination of phases with particular morphologies, good room temperature ductility can be obtained not only by compression and bending tests but also by tensile tests. Such a strategy has been so far most successful in the Co-Al-Ni-Ti system, where room temperature ductility of near to 20% is achieved in a B2/L1(2)/(Co,Ni) three-phase alloy. It is pointed out that keys to design ductile multi-phase intermetallic alloys would be: (1) refinement of the microstructure utilizing solid state phase transformations such as an invariant reaction; (2) adjustment of amounts and compositions of the constituent phases, which is not possible in the binary system, but is in a multi-component system, and (3) hot fabrication to reduce solidification defects. Copyright (C) 1996 Elsevier Science Ltd.
  • S MIURA, JA HORTON, CT LIU, T SUZUKI, Y MISHIMA
    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 192 769 - 773 0921-5093 1995/02 [Refereed][Not invited]
     
    Ni3Al single crystals with the L1(2) structure and with a [123] orientation with respect to the stress axis were deformed by compression at temperatures above T-p, the yield stress peak temperature, so that (001) cube slip dislocations were introduced. The dislocation morphology, configuration and density on (001) slip planes were examined as functions of the deformation temperature, strain rate and strain by transmission electron microscopy. It was found that dislocations on the cube plane were predominantly of edge character and that within the range studied the dislocation density was largely independent of the deformation temperature, strain rate and strain.
  • Microstructure and mechanical properties of the L12/L21 two-phase alloys in the quaternary Co-Al-Ni-Ti system
    Takeo Matano, Yoshisato Kimura, Seiji Miura, Yoshinao Mishima
    Materials Research Society Symposium - Proceedings 364 (2) 1377 - 1382 0272-9172 1995 
    An attempt is made to develop a two-phase alloy consisting of the L12 and L21 (Heusler) phases in the Co-Al-Ni-Ti quaternary system exhibiting a high elevated temperature strength as well as some room temperature ductility as a new class of heat resisting structural materials. The idea behind this approach is expectations for the L21 phase to provide high elevated temperature strength, whereas the L12 phase provides some room temperature ductility. Compositional optimization in the room temperature ductility of the L12 (Co,Ni)3(Al,Ti) is first carried out and then, based on the result, several L12/L21 two phase alloys are designed. It is found that a few to several per cent room temperature bend ductility is obtained in such two-phase alloys.
  • Y KIMURA, M TAKAHASHI, S MIURA, T SUZUKI, Y MISHIMA
    INTERMETALLICS 3 (5) 413 - 425 0966-9795 1995 [Refereed][Not invited]
     
    The Co-Al-C ternary phase diagram has been experimentally examined for the Co-corner with a particular interest in phase relations among cobalt primary solid solutions, denoted as (Go), the E2(1) type intermetallic compound Co3AlC, and the B2 type CoAl. Liquidus surface composed with monovariant and contour lines, and corresponding reaction scheme were determined by optical microscopy, differential thermal analysis, X-ray diffraction, and energy dispersive X-ray spectroscopy. Several isothermal sections and isoplethals with respect to a fixed concentration for one of the elements were also evaluated. It is shown that such multiphase alloys as B2/E2(1), B2/(Co), and B2/E2(1)/(Co) can be produced in the ternary system by proper choices of alloy chemistry and heat treatment.
  • JY Park, MH Oh, DM Wee, S Miura, Y Mishima
    GAMMA TITANIUM ALUMINIDES 377 - 384 1995 [Refereed][Not invited]
  • Y KIMURA, M TAKAHASHI, S MIURA, Y MISHIMA
    HIGH-TEMPERATURE ORDERED INTERMETALLIC ALLOYS VI, PTS 1 AND 2 364 1371 - 1376 0272-9172 1995 [Refereed][Not invited]
  • E Kobayashi, K Shinmoto, S Miura, T Suzuki, Y Mishima
    GAMMA TITANIUM ALUMINIDES 347 - 352 1995 [Refereed][Not invited]
  • S MIURA, Y MISHIMA
    HIGH-TEMPERATURE ORDERED INTERMETALLIC ALLOYS VI, PTS 1 AND 2 364 561 - 566 0272-9172 1995 [Refereed][Not invited]
  • Takahiro Matsuo, Hideki Hosoda, Seiji Miura, Yoshinao Mishima
    Materials Research Society Symposium - Proceedings 364 855 - 860 0272-9172 1995/01 [Refereed][Not invited]
     
    Intermetallic alloys based on the L12 Ni3(Al,Be) phase in the ternary Ni-Al-Be system are prepared so that the alloys are multi-phase with the B2 intermetallic compound NiBe and a Ni primary solid solution denoted as (Ni). Such three-phase alloys, Ni-16 to 20 at%Al-10 at%Be, exhibit good room temperature ductility as measured by four-point bending. In order to examine the phase stabilities and relations among constituent phases, a vertical section of the ternary system is constructed at a constant 10 at%Be mainly by differential thermal analysis. It is found that improvement in room temperature ductility can be achieved by the formation of a fine mixture of constituent phases during invariant reactions during solidification, which is further enhanced by the co-existence of the L12 phase formed as the primary solidification phase.
  • Y KIMURA, S MIURA, T SUZUKI, Y MISHIMA
    MATERIALS TRANSACTIONS JIM 35 (11) 800 - 807 0916-1821 1994/11 [Refereed][Not invited]
     
    Various two- or three-phase alloys were prepared based on the B2 intermetallic compound CoAl in the Co-Al-Ni ternary system, in which the B2 phase forms a continuous solid solution with NiAl of the same ordered structure. Combination of the phases with the B2 phase can be the (Co, Ni) primary solid solution phase being also continuous from Co to Ni-corners, and/or the L1(2) phase based on Ni3Al. Then the relationship between microstructure and mechanical properties were systematically investigated by optical and transmission electron microscopy and by micro-Vickers hardness and compression tests. It is found that two-phase alloys of B2/Ll(2) show superior room temperature ductility with over 10% plastic strains to those of B2/(Co, Ni). The present work is based on the seemingly ever lasting motivation to provide some ductility to the intrinsically brittle CoAl compound which unless otherwise has attractive properties as a new high-temperature structural material.
  • 三島 良直, 三浦 誠司, 鈴木 朝夫
    日本航空宇宙学会誌 日本航空宇宙学会 42 (489) 605 - 609 0021-4663 1994/10 [Refereed][Not invited]
  • Y KIMURA, S MIURA, T SUZUKI, Y MISHIMA
    EXPERIMENTAL METHODS OF PHASE DIAGRAM DETERMINATION 113 - 121 1994 [Refereed][Not invited]
  • S MIURA, CT LIU
    INTERMETALLICS 2 (4) 297 - 313 0966-9795 1994 [Refereed][Not invited]
     
    The effects of aluminum concentration and green compact thickness on the reaction synthesis of powder compacts containing 25 to 40 at. %Al were studied under a uniaxial compressive stress of 10 MPa. The results indicate that both reaction product and material density are sensitive to these two parameters. For all powder compacts with a thickness of 5 mm, no temperature increase was detected during reaction synthesis, indicating no formation of transient liquid phases and thus no self-sustaining combustion reaction. For 6- and 7-mm-thick compacts containing 40% Al, a full synthesis reaction took place, resulting in production of the NiAl alloy with a high material density (>98%) and a fine grain size (14 mum). Other compacts containing 25 and 30% Al showed a coexistence of partially and fully reacted zones, with the reaction zone size strongly dependent on aluminum concentration and compact thickness. All the results are discussed in terms of local heat accumulation and heat transfer as well as thermodynamic analyses of exothermic reactions during each reaction step.
  • Yoshinao Mishima, Seiji Miura, Takahiro Matsuo, Hideki Hosoda
    Proceedings of the TMS Fall Meeting 191 - 197 1994 [Refereed][Not invited]
     
    Development of microstructure is examined in a Ni-20at%Al-10at%Be alloy based on the L12 phase having the B2 NiBe as a second phase. To be consistent with the information on the isothermal section reported previously, a vertical section at a constant 10 at%Be is constructed mainly by differential thermal analysis. The microstructures of as-cast and annealed alloy specimens are discussed with the isoplethal obtained, and then the possibility for the Ni-primary solid-solution phase to co-exist as a third phase is suggested. It is also shown that a fine mixture of the L12 and the B2 phases may arise from two invariant reactions occurring during solidification. Then room-temperature mechanical properties are evaluated by tensile, bending and compression tests to reveal that the alloy exhibits excellent ductility.
  • Design of Ductile Ni3Al Being Two Phase with NiBe
    Y. Mishima, S. Miura, T. Suzuki, T. Matsuo, H. Hosoda
    Alloy Modeling and Design, TMS 275 - 282 1994 [Refereed][Not invited]
  • Development of Ductile Polycrystalline Ni3Al by Microstructural Control
    H. Hosoda, S. Miura, T. Suzuki, Y. Mishima
    3rd Jpn Intl. SAMPE Symp., Intl. Symp. Intermetallic Compounds for High-Temperature Structural Applications 1193 - 1197 1993 [Refereed][Not invited]
  • S MIURA, M KOIKE, Y MISHIMA, T SUZUKI
    JOURNAL OF THE JAPAN INSTITUTE OF METALS 56 (11) 1343 - 1351 0021-4876 1992/11 [Refereed][Not invited]
     
    The plastic behavior of Ni3 (Si, Ti) single crystals with 10 at%Ti is investigated, and the effects of temperature, strain-rate and crystallographic orientation with respect to stress axis are examined. An appreciable orientation dependence of critical resolved shear stress (CRSS) is found at 77 K, where the CRSS increases as the orientation shifts from [001] toward [111BAR]. The apparent activation energy for the positive temperature dependence of strength, U, is evaluated to be 7.1 to 7.7 kJ/mol which is smaller than Ti free Ni3Si and is in good agreement with that expected from the data in polycrystals. For orientation near [001], where the octahedral viscous flow governs the steady-state deformation following characteristic yield drop, the stress exponent is found to be about 7 which is considerably higher than the values of 3.5-5 in other L1(2) compounds. The decrement in CRSS by the yield drop is unusually small as compared to the other L1(2) single crystals. The activation energy for the steady-state deformation is evaluated to be comparable to the value for diffusion of Si in Ni3Al. A good oxidation resistance of the alloy is also made clear in the present work.
  • S MIURA, M KOIKE, K WANG, Y MISHIMA, T SUZUKI
    JOURNAL OF THE JAPAN INSTITUTE OF METALS 56 (10) 1207 - 1213 0021-4876 1992/10 [Refereed][Not invited]
     
    In order to make a comparison of the plastic behaviour between Ni3Al and Ni3Ge, where Al is a 3B and Ge a 4B-subgroup element, effects of temperature, orientation and strain-rate on the temperature dependence of strength are investigated in Ni3Ge single crystals with 76 at%Ni. It is found that at 77 K there is an appreciable orientation dependence in compressive 0.2% flow stress. For orientation near [111BAR], the onset of cube slip is found to occur at as low as ambient temperature which is unusual for the L1(2) single crystals. The thermal component of critical resolved shear stress for the cube slip vanishes also at a much lower temperature and the athermal component is found to exhibit a slight negative temperature dependence arising from the temperature dependence of shear modulus. For orientation near [001] and at the temperatures above the peak, the characteristic yield drop and the following steady-state deformation are found as in other L1(2) intermetallic compounds. The activation energy for the steady-state deformation is found to be 277 kJ/mol mol which is reasonably in good agreement with the value for the diffusion of Ge in Ni3Ge.
  • S MIURA, Y MISHIMA, T SUZUKI
    JOURNAL OF THE JAPAN INSTITUTE OF METALS 56 (10) 1200 - 1206 0021-4876 1992/10 [Refereed][Not invited]
     
    The temperature, strain-rate and orientation dependences of strength are investigated in single crystalline Ni3 (Al, 5.0Si), and the results are compared with those on Ni3 (Al, 2.5Si) single crystals reported previously by the present authors. The magnitude of the anomalous positive temperature dependence of strength is found to increase with increasing Si additions and the value of activation energy to yield the mechanical anomaly is found to be in good accordance with that being predicted from the data for polycrystals. For an orientation near [111BAR], where the cube slip governs the plastic behaviour above the peak temperature, the temperature and strain-rate dependences of strength are found to differ considerably from what was found in Ni, (Al, 2.5Si). This is shown to be caused by the difference in the deviation from stoichiometry and not by the difference in Si content of the alloys. On the other hand, the steady-state deformation behaviour being governed by the octahedral viscous flow for the orientation near [001] resembles that in Ni3(Al, 2.5Si), where the stress exponent as well as the activation energy for the deformation is found to be nearly identical. The activation energy evaluated is of the same order as that for diffusion of Si in Ni3Al.
  • S MIURA, Y MISHIMA, T SUZUKI
    JOURNAL OF THE JAPAN INSTITUTE OF METALS 56 (10) 1214 - 1220 0021-4876 1992/10 [Refereed][Not invited]
     
    The temperature, orientation and strain-rate dependences of strength are investigated in single crystalline Ni3Al-4Cr (74 at%Ni-22 at%Al-4 at%Cr) in which Cr substitutes both Ni and Al sites. It is found that the solid solution hardening evaluated at 77 K by Cr addition is small and that the activation energy for the thermally activated cross slip yielding the mechanical anomaly becomes slightly larger by the addition. In the temperature range and for an orientation near [111BAR] where cube slip governs the plastic deformation, the athermal component of the critical resolved shear stress (CRSS) is evaluated to be as small as 40 MPa, whereas the thermal component at 0 K is estimated to be 2250 MPa being as large as the value reported for the Ni-rich Ni3Al single crystals. For an orientation near [001], where the octahedral viscous flow governs the plastic behaviour, the activation energy for the steady-state deformation is evaluated to be 317 kj/mol which is in good agreement with the value for diffusion of Cr in Ni3Al. It is also found that the oxididation resistance of Ni3Al-4Cr is superior to Ni3 (Al, 5.0Ti) but is inferior to Ni3 (Al, 5.0Si). It is concluded, therefore, that the stoichiometry of Ni3Al-Cr cannot be made unequivocally.
  • S MIURA, H KURIYAMA, Y MISHIMA, T SUZUKI
    JOURNAL OF THE JAPAN INSTITUTE OF METALS 56 (8) 943 - 951 0021-4876 1992/08 [Refereed][Not invited]
     
    Single crystalline Co3Ti base quarternary compounds, (Co, Ni) 3 (Ti, Al), are prepared and the effects of temperature, strain rate and orientation on the plastic behavior are investigated. Then the results are compared to other L1(2) intermetallic compounds being represented by Ni3Al. The differences found by the comparison are as follows. (1) Regardless of the crystallographic orientation with respect to the stress axis, there is a strong negative temperature dependence of strength at low temperature regime. (2) Plastic deformation is accompanied by serration on the stress strain curve and by metallic acoustic emission in the single crystals with near-[111] orientation and at temperature regime between 77 to 973 K where the anomalous positive temperature dependence of strength is observed. (3) For the same orientations, the temperature regime where cube slip governs the plastic deformation is narrow. (4) Octahedral viscous flow at the high temperature regime is not associated with well-defined yield drop. It is to be noted that the plastic behavior of Co3Ti base single crystals should also be discussed seperately in the above four regimes as has been done in other single crystalline L1(2) compounds.
  • S MIURA, CT LIU
    SCRIPTA METALLURGICA ET MATERIALIA 26 (11) 1753 - 1758 0956-716X 1992/06 [Refereed][Not invited]
  • S. Miura, K. Mitsui, Y. Tanaka, Y. Mishima, T. Suzuki
    Philosophical Magazine A: Physics of Condensed Matter, Structure, Defects and Mechanical Properties 65 (3) 737 - 747 0141-8610 1992 [Refereed][Not invited]
     
    The composition and temperature dependences of strength of ordered and disordered single crystalline Cu3Pt alloys involving ternary additions are investigated. The relation between deformation behaviour and relative phase stability of L12 ordered phase with respect to L12−s long period ordered phase is discussed in relation to the antiphase domain (APD) morphology observed in each alloy. Direct observation of APDs by transmission electron microscopy shows that maze-like APDs are formed during ordering in Cu-23at.%Pt alloy, while in (Cu-23at.%Pt)-1 at.%In and Cu-19at.%Pt alloys swirl-like APDs are formed. This implies that the relative phase stability of L12 phase with respect to L12− phase in Cu-23 at.%Pt alloy is lower than that in (Cu-23at.Pt)-l at.%In and Cu-19at.%Pt alloys. Compression tests of an ordered single crystal of each alloy at various temperatures reveal a positive temperature dependence of critical resolved shear stress (CRSS) in Cu-23 at. %Pt alloy, but not in (Cu-23 at.%Pt)-1 at.%In and Cu-19at.%Pt alloys. Also, it is shown that disordered Cu-23 at.%Pt alloy dose not exhibit the positive temperature dependence of the CRSS. On the basis of these facts, it is demonstrated that the Kear-Wilsdorf mechanism involving thermally activated cross slip from the (111) primary glide plane to (010) non-glide plane is responsible for the positive temperature dependence of strength in ordered Cu-23 at.%Pt alloy. © 1992 Taylor & Francis Group, LLC.
  • T SUZUKI, Y MISHIMA, S MIURA
    MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING 146 (1-2) 245 - 260 0921-5093 1991/10 [Refereed][Not invited]
     
    All the available shear stress data for various kinds of L1(2) single crystals which have been reviewed in 1989 are revised with the recent progress obtained with the last 2 years. Most of the findings in that review are strengthened further by the introduction of new data. Besides this, it is pointed out that the shear stress of L1(2) compounds such as Ni3Ge and Ni3Si with a strong positive temperature dependence of strength have a tendency not to obey Schmid's law at low temperatures. At elevated temperatures, it is shown that the relation between shear stress and shear strain for the steady state stress obtained in the constant-strain-rate test and the strain rate obtained in the constant-load test, i.e. the creep test, can be expressed by a single straight line. The composition dependence of the creep resistance in Ni3Al is the most interesting result found. The creep resistance increases with increasing nickel concentration on both sides of stoichiometry but the value extrapolated to stoichiometry from the nickel-rich side is much larger than that extrapolated from the aluminium-rich side. The problems which must be solved in this field are suggested.
  • S MIURA, Y MISHIMA, T SUZUKI
    ZEITSCHRIFT FUR METALLKUNDE 80 (3) 157 - 163 0044-3093 1989/03 [Refereed][Not invited]
  • S MIURA, Y MISHIMA, T SUZUKI
    ZEITSCHRIFT FUR METALLKUNDE 80 (3) 164 - 169 0044-3093 1989/03 [Refereed][Not invited]
  • 三島 良直, 三浦 誠司, 鈴木 朝夫
    熱処理 日本熱処理技術協会 29 (1) p19 - 24 0288-0490 1989/02 [Refereed][Not invited]
  • S MIURA, Y MISHIMA, T SUZUKI
    ZEITSCHRIFT FUR METALLKUNDE 80 (2) 112 - 117 0044-3093 1989/02 [Refereed][Not invited]
  • S MIURA, Y MISHIMA, T SUZUKI
    ZEITSCHRIFT FUR METALLKUNDE 80 (1) 48 - 52 0044-3093 1989/01 [Refereed][Not invited]
  • S MIURA, S OCHIAI, Y OYA, Y MISHIMA, T SUZUKI
    HIGH-TEMPERATURE ORDERED INTERMETALLIC ALLOYS III 133 341 - 346 1989 [Refereed][Not invited]
  • T SUZUKI, Y MISHIMA, S MIURA
    ISIJ INTERNATIONAL 29 (1) 1 - 23 0915-1559 1989 [Not refereed][Not invited]
  • S MIURA, S OCHIAI, Y OYA, Y MISHIMA, T SUZUKI
    JOURNAL OF THE JAPAN INSTITUTE OF METALS 51 (5) 400 - 406 0021-4876 1987 [Refereed][Not invited]
  • S OCHIAI, S MIURA, Y MISHIMA, T SUZUKI
    JOURNAL OF THE JAPAN INSTITUTE OF METALS 51 (7) 608 - 615 0021-4876 1987 [Refereed][Not invited]

MISC

Books etc

  • 渡辺義見, 三浦博己, 三浦誠司, 渡邊千尋 (Joint work)
    コロナ社 2010/02 (ISBN: 4339046051) 232
  • 図でよくわかる機械材料学
    コロナ社 2010
  • 実験力学ハンドブック
    日本実験力学会 2008
  • よく分かる実験技術・学術用語
    日本実験力学会 2006

Presentations

Association Memberships

  • 日本実験力学会   ASM   学振172委員会合金状態図   ＴＭＳ   日本鉄鋼協会北海道支部   日本金属学会北海道支部   日本熱処理技術協会   ＭＲＳ   日本鉄鋼協会   日本金属学会   The Japanese Socity for Experimental Mechanics   ASM   

Research Projects

  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
    Date (from‐to) : 2018/06 -2023/03 
    Author : 阿部 英司, 中島 英治, 河村 能人, 相澤 一也, 藤居 俊之, 斎藤 拓, 山崎 倫昭, 染川 英俊, 萩原 幸司, 君塚 肇, 三浦 誠司, 伊藤 浩志, 榎 学, 寺田 大将, Stefanus Harjo
     
    本総括班の目的は，ミルフィーユ構造のキンク強化理論の確立と新材料創製を目指して，司令塔として領域研究の組織的かつ有機的な運営を実施することである．初年度の主な実績は以下の通りである． (1) より効率的な領域運営のため，総括班体制を一部修正し，スリム化を図った．(2) 領域キックオフ会議，および年度成果報告会を企画・開催し，領域内での研究活性化と，研究者間の連携強化に努めた．(3) 異分野間の連携強化のため，各計画研究班内，および各計画研究班間の勉強会や研究会を積極的に企画・開催した．(4) 学協会におけるシンポジウムを複数企画し，研究成果の発信に務めた．(5) 広報活動の一環として，本新学術の内容紹介リーフレット，および第１号ニュースレターを刊行し，各学協会や各大学・研究機関に配布した，リーフレット配布は公募研究募集に非常に有効であった．(6) 知的財産の重要性認識のため，領域メンバーを対象として特許専門家による講演会を実施し，特許申請を促した，(7) 若手人材育成部会が中心となり，大学院生・若手研究者を主体とする合宿研究会を企画・開催した.(8) 研究活動支援部会より，Mg合金系の共通試料の提供を開始した，(9) 領域研究のホームページを立ち上げ，領域研究内容の情報発信に務めた．(10) 本新学術が主催する国際会議を企画・開催し，海外の評価委員数名を含めて本新学術の方向性の議論を深めた．
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
    Date (from‐to) : 2018/06 -2023/03 
    Author : 三浦 誠司, 江村 聡, 藪 浩, 斎藤 拓
     
    ミルフィーユ構造物質（MFS）を下記(a)-(c)の三種類に区分し、物質探索を行った。 (a) 結晶構造型MFSはLPSO相、MAX相、高分子系を含み、典型的層間隔はnmオーダーである。 (b)組織制御型MFSはAl基やTi基などの二相合金を含み、典型的層間隔はμｍオーダーである。 (c)ハイブリッド型MFSはLPSO―Mg合金、V-V2AlC合金などを含み、組織制御型MFSの構成相の一方が結晶構造型MFSである物質と定義した。 これらに関して下記のような研究展開が得られており、既に論文、特許などへの展開が進行中である。 （１）金属系MFSの創製：(1-1) Al-Ag系やNi-Sn合金において，面心立方構造と六方最密構造の二相が共通のすべり面を持つことから，ミルフィーユ構造を実現できる合金系が見出された。(1-2) ミルフィーユ構造を持つTi-Cr系合金について圧縮試験や冷間圧延によってキンク変形が導入されることを見いだした。 （２）高分子系MFSの創製：(2-1)高分子膜上にシリカ前駆体を塗布し、UV-O3処理で高分子ーシリカ積層ミルフィーユ構造の作製に成功した。高分子ーシリカ複合体をMg蒸気中で処理することで、Mg2Siとカーボンの積層構造が形成できることも明らかとした。ブロック共重合体から形成したミルフィーユ構造に圧縮を加えることでキンク状構造を導入できることが明らかとなった。特殊な蛍光プローブを分子内に導入し、力学強度を可視化する高分子合成に成功した。(2-2) 結晶性高分子のポリエチレンに対して配向制御法を駆使して巨視的なミルフィーユ構造を形成させることで、降伏を抑制して著しく高強度化できることを見出した。 （３）セラミックス系MFSの創製：MAX相を金属母相と組み合わせたMFS（V-V2AlC）において、添加元素による積層界面安定化効果が明らかとなった。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2019/04 -2022/03 
    Author : Miura Seiji
     
    The aim of this research is to establish the experimental method for the in-situ observation of crack formation in multi-phase materials during the indentation though a transparent indent made of sapphire or diamond. This apparatus enables us to understand the time-dependent evolution of cracks and deformation around the indents.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2016/04 -2020/03 
    Author : Ikeda Ken-ichi
     
    In this study, in order to clarify the influence of elements of grain boundary segregation and solid solution on the mechanical property and the recrystallization behavior of poly crystalline metals, the development of the bicrystal fabrication method and the elucidation of properties of grain boundaries were carried out. The main results are as follows. (1) We designed the new mold suitable for Bridgeman Method and succeeded in the fabrication of pure aluminum bicrystals. (2) The precipitation and recrystallization behavior of Al-Mn alloys were strongly affected by the temperature of hot working process and the additional elements. (3) In Al-Mg-Si alloys, the grain boundary character affects the aging precipitation behavior and the mechanical properties.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
    Date (from‐to) : 2011/04 -2016/03 
    Author : Okuda Hiroshi, IIKUBO Satoshi, MIURA Seiji, OHTANI Hiroshi, ODE Machiko, TOKUNAGA Tatsuya
     
    In-situ small- and wide- angle scattering / diffraction method with a use of multicolor X-rays has been successfully developed and applied for the transformation kinetics of Mg85Y9Zn6 ingot. These in-situ measurements and experimental phase digagram studies revealed that the LPSO structures can be understood as 'phases' and the phase transition process in MgYZn is unique ｉｎ that it was initiated by phase separation under mixing instability, but further driven by structural phase transformations.
  • 耐火金属基BCC高濃度固溶体をベースとした超耐熱材料創成
    JST：ALCA
    Date (from‐to) : 2014/10 
    Author : MIURA Seiji
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2011 -2013 
    Author : MIURA SEIJI, SAKAIRI Masatoshi
     
    In order to fabricate a bulk material composed of nano-sized layers as a new kind of nano-materials, electro-depositing (plating) process is used. An equipment is developed to accumulate more than 100 layers by immersing into different solutions alternately to deposit different metallic layers such as copper and nickel. TEM and SEM are mainly used to investigate the microstructure of samples, and it was found that the layers are coherent each other. Many grain boundaries and twin boundaries are found in the layers, which may cause a fast diffusion of elements.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2008 -2010 
    Author : WATANABE Seiichi, YASUDA Hidehiro, NIWASE Keisuke, NISIGUCHI Norihiko, OHSASA Kenichi, MIURA Seiji, SAKAGUCHI Norihito, YATSU Shigeo, KUROKAWA Kazuya, AKIYAMA Tomohiro
     
    Submerged glow-discharge plasma has been researched as a method of nanoparticles (nanoballs) synthesis method. We discovered the formation of metallic nanoballs during plasma electrolysis in 2007. The product that was obtained from the electrolyte plasma electrolysis was found to be uniformly-shaped spherical nanoballs. In this research, we investigate possible applications of the method to functional devise fabrication.
  • Ministry of Education, Culture, Sports, Science and Technology：Grants-in-Aid for Scientific Research(基盤研究(A))
    Date (from‐to) : 2007 -2009 
    Author : Seiji MIURA, 木村 好里, Tetsuo MOHRI, Seiichi WATANABE, Kenichi OHSASA, Yoshinao MISHIMA, Satoshi TAKIZAWA, Yoshisato KIMURA
     
    It was found that a proper microstructure composed of Nb and Nb_5Si_3 was obtained by heat treatment of an Nb-18.1Si-1.5Zr alloy uni-directionally solidified with a rate as high as 1500mm/h. Three-dimensional imaging revealed that large Nb grains are formed through the above-mentioned technique. The alloy shows a room temperature compressive ductility of about 2% and the propagation of cracks in brittle Nb_5Si_3 phase is suppressed by surrounding ductile Nb. Ta addition is required to keep the phase transformation route for the microstructure control with addition of Mo and W for strengthening Nb phase which governs the high temperature deformation behavior.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2001 -2003 
    Author : MOHRI Tetsuo, MIURA Seiji
     
    Down quenching in a common operation employed in materials science and technology communities both to investigate the kinetics of phone transition and to realize new structural and functional properties. In the present study, we focused on the reverse operation, namely the up-quenching operation, and we attempted to clarify the stability and phase transition kinetics of a low temperature ordered phone both theoretically and experimentally. Particular focuses were placed on ; (1) phase transition behavior below an above the spinodal disordering temperature, and (2) detection and interpretation of Retro effect. We first performed the theoretical calculations based on Cluster Variation Method and Path Probability Method and suggested that the spinodal disordering in a common phenomenon for an order-disorder system of first-order transition. Further theoretical studies based on the Phase Field Method clarified the microstructural evolution kinetics of Anti phase boundary during the relaxation process, and by combining with the FLAPW electronic structure calculations, more realistic calculations for the microstructural topology of Anti Phase boundary was performed for Fe-Pd system. The present experimental investigations are classified into two major categories. One is the detection of spinodal disordering temperature for Ni-Mo system and the other is the clarification of the mechanism of Retro effect for Cu-Au system. For the former, anomaly was detected for both the electrical resistivity and the coefficient of thermal expansion when the heating rate is accelerated. For the latter, combined with Laser Microscopy, the evolution and devolution of the surface morphology is carefully observed upon heating and cooling. We concluded that the Retro effect is associated with internal stresses originated from the constraint due to the discontinuity of grain boundaries.
  • Thermal expansion measurement of micron size small spesimens
    Date (from‐to) : 2002
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 1996 -1997 
    Author : MISHIMA Yoshinao
     
    There have been several examples in which the control in the microstructure consisting of intermetallic phases with different ordered crystal structure which are neighboring in the multi-component alloy systems was successful to provide appreciable tensile ductility at room temperature. However it seems in those cases to be difficult to achieve enough high temperature strength at the same time due to the instability of a fine microstructure at elevated temperatures. The present work is designed to develop multi-phase intermetallic alloys through a phase decomposition at a high enough temperature so that a microstructure produced would be stable at temperatures over 1273 K.The Ni-Al-Mo system was chosen as an alloy system because there seems to be a compositional region in which the B2 phase decomposes into the Ll_2 Ni_3Al and the alpha-Mo terminal solid solution, alpha(Mo), at around 1573 K.Phase diagram evaluation by differential thermal analysis and microstructural observation is followed by fabrication of selected alloys by arc-melting. It is then shown that some alloys, typically aNi-22at%Al-8at%Mo alloy, exhibits an excellent high temperature strength with some room temperature ductility.
  • 文部科学省：科学研究費補助金(奨励研究(A))
    Date (from‐to) : 1996 -1996 
    Author : 三浦 誠司
     
    本研究では、相の関係や不変形反応相互の関係を整理・分類し、場合分けを行うことにより、3元系状態図について半自動的な決定や、既往の状態図のチェックが可能なアルゴリズムの構築を目指した。具体的には、3元系状態図が3相三角形によって分割されていることから、これを相の数と等しい角数の多角形に変換し、その多角形を三角形で分割する。固相から成る3相三角形は必ず4相平衡と対応しており、液相の関与した3種類の3相平衡がある温度で合する。それら3種類の3相平衡は2元系の共・包晶を始点もしくは終点としており、液相の組成の温度による変化を示した線により表すことができる。4相平衡も同様に液相の組成変化を表す線の結合によって表すことができるが、これらの線の連結はグラフ理論により隣接行列として記述できる。あり得る三角形分割および各平衡の温度の上下関係は行列式を簡単な手順で操作することで列挙できる。さらに、隣接行列の演算により、すべての3および4相平衡点の関係、すなわち温度の上下関係を記述でき、その上下関係を既往のデータと比較することにより、あり得ない組合せを排除することができる。本研究では3元化合物の存在しない系について、(1)既知の2元系状態図から、あり得る反応経路図を列挙し、(2)状態図に関する実験的研究結果・熱力学的計算結果などから得られる限定条件を盛り込むことにより、反応経路図を絞り込む、という、今後の拡張のための原型となるアルゴリズムを実現した。組合せ総数は相の数が8程度と比較的少ない場合でも100万通りを越すことから、大量のデータを迅速に処理し、かつ保存できる必要があると同時に、アルゴリズム上の工夫によって全てを計算し照合するのではなく、ある程度実験結果から計算条件を限定することを行った。これにより、計算総数を大幅に圧縮することが可能となり、最適の場合2桁もの減少が見込める。
  • マグネシウム合金単結晶及び複合材料の変形挙動
    民間学術研究振興費補助金
    Date (from‐to) : 1996
  • mechanical properties of Mg-based alloys
    Grant-in-Aid for Promotion of Private Scientific Research
    Date (from‐to) : 1996
  • Improvement of mechanical properties of Nb-Si based intermetallic compound-based materials by microstructure control
    Grant-in-Aid for Scientific Research
    Date (from‐to) : 1995
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1994 -1994 
    Author : 三島 良直, 三浦 誠司
     
    金属元素の中で最も軽量であるベリリウムを構成元素とする金属間化合物の中で、その規則構造の対称性が最も高く、よって室温での塑性変形能が期待できる NiBeとCoBeを対象として、それぞれの構成元素による2元系Ni-Be、Co-Be状態図上で隣接するNiあるいはCo1次固容体相(以後、(Ni)あるいは(Co)と表記)との複合組織化により機械的性質の改善を試みた。その結果、NiBe/(Ni)1次固容体の2相合金は(Ni)相の微細分散により550K付近で著しく高い強度を示すものの、その強度は試験温度上昇とともに急激に低下してしまうこと、また室温付近ではほとんど延性を示さないことが明らかとなった。一方、CoBe/(Co)合金においては、数種の異なる合金組成においてすべて室温から高温まで良好な延性を示すことが見いだされた。また、この合金は中音度域で強さの逆温度依存性を示したが、これはL1_2型金属間化合物を代表とする一群の化合物にみられる転位の熱活性化運動による可逆的な過程によるものとは異なり、機械試験中に起こる組織変化によって生じる非可逆的な現象であることを示した。 本研究の結果、特にCoBe/(Co)2相合金においては良好な室温延性がえられることから構造用金属間化合物としての応用への可能性があることが明らかとなったが、今回の実験範囲では1000℃での高温強度は低く、室温延性を損なわずに高温強度を高めるためのさらなる合金設計が必要であると考えられる。
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1993 -1994 
    Author : 三島 良直, 安田 健, 三浦 誠司
     
    実用Ni基超合金の性能を超える新しい耐熱構造用材料の候補として金属間化合物Ni_3A1が挙げられるが、その多結晶合金は粒界脆性を示し、その克服にむけて多くの研究がなされている。本研究では粒界脆性の危惧のない単結晶Ni_3A1を対象とし、その高温強度をいかにして高めるかという観点からの合金設計を目的として平成5年度より2年間にわたって行った。 初年度においては研究代表者ならびに分担者によってこの目的に有効な添加元素であることが見いだされているHfの添加量、ならびに単結晶の結晶方位が高温クリープ抵抗におよぼす影響を検討し、さらにHfとならぶ耐火金属元素であるW、Nb、Taなどの添加の効果についても系統的な研究を行った。定常クリープ速度、応力指数、拡散クリープにおける活性化エネルギーの大小等の比較を行った結果、これら元素のクリープ抵抗の増加への寄与の順列を見いだすとともに、単結晶Ni_3A1のクリープ強度が従来いわれている(001)方位ではなく、(011)方位で最も高い場合があることを見いだした。また、次年度ではこれら元素の複合添加の効果を結晶方位の影響とともに調べ、(011)方位の単結晶における複合添加の有効性を定量的に示すことが出来た。
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1993 -1993 
    Author : 三島 良直, 三浦 誠司
     
    本研究の目的は、現在のNi基実用耐熱合金におけるLl_2型金属間化合物Ni_3Al析出相に対応する析出相をCo基耐熱合金に導入することで、より優れた耐熱性を付与することである。 高融点の析出相として主にCo基合金に導入を図ったのは、E2_1型金属間化合物Co_3AlCで、Ni基耐熱合金の析出強化相Ni_3Alの結晶構造であるLl_2型規則構造に炭素(C)が侵入した形態を有している。Co-Al-C系の状態図は不確定であったため、まずCo近傍のCo-Al-C三元状態図を確定することに努めた。Ar雰囲気中で非消耗型アーク溶解装置によって種々の合金を溶製し、X線、示差熱分析、光学顕微鏡等による組織観察などを行い、既存の状態図に修正を施した。修正した状態図に基づいていくつかの合金を選定し、その高温変形強度を測定した。また、隣接相であるB2型金属間化合物CoAlも同時に導入を試み、Co-Co_3AlC2相及びCo-Co_3AlC-CoAl3相合金の比較も行った。その結果、B2型金属間化合物CoAlを含むものは、必然的にAl量も多く、耐酸化性、比重などの点で有利と考えられるが、高温における強度の点では2相合金の方が有望であることが判明した。修正した状態図から、Co合金中のCo_3AlC量はNi基超合金中におけるNi_3Alほど多くすることは困難であると考えられるが、わずかな量のCo_3AlCをCoに導入することで、Ni基超合金に比肩する高温強度を得ることができる可能性が示された。 さらに、いくつかの合金については室温大気中で圧延を試みた。その結果、いくつかの組成で、10%以上の圧延が可能であった。
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1993 -1993 
    Author : 加藤 雅治, 三浦 誠司, 三島 良直
     
    本研究の目的は、次世代の高温耐熱構造用材料として期待されているLl_0型金属間化合物TiAlに、同じ面心立方構造を基本構造としていて、その格子定数やその比であるc/aも近い、Al-rich側に存在するDO_<22>型金属間化合物Al_3Tiを整合、もしくは半整合析出分散させることで、必ずしも十分な高温変形強度を有しているとはいえないTiAl金属間化合物に対して比強度の高い、効果的な析出強化相を導入する可能性を探ることである。 両相はTi-Al2元系では隣接しないため、本研究ではまずTi-Al-Nb3元系のAlコーナー近傍における相領域や融点、固相反応を明確にした。その結果、広い組成範囲で(Ti,Nb)AlとAl_3(Ti,Nb)は平衡していること、その大部分の領域の初晶はAl_3(Ti,Nb)であることが判明した。また、熱処理により、初晶Al_3(Ti,Nb)および(Ti,Nb)Al両相中に互いが析出することが確認された。このことは、TiAl単相中に、Al_3Tiを析出させ得ることを示唆する。2相領域での硬さ試験を行ったところ、熱処理によって硬さは上昇しているが、上昇量が特に大きい領域があり、その組成は決まったTie-Line上に存在することから、この平衡組成近傍はTiAl、Al_3Tiいずれの単相合金にも熱処理によって第2相を析出させて機械的性質を向上させうる可能性が高いものと考えられる。
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1991 -1992 
    Author : 三島 良直, 毛利 哲夫, 三浦 誠司, 加藤 雅治
     
    これまでにCo-A12元系B2/(Co)2相合金で圧縮塑性歪2〜3%,Co-A1-Ni3元系B2/L1_2(Ni_3A1)2相合金で10%以上の延性改善を行った。B2/L1_2相合金では延性と高温強度を同時に改善できる可能性があり,Co-A1-Ni-Ti4元系内でL1_2 Ni_3A1とCo_3Tiの連続固溶体を利用すると,Co高濃度側までB2/L_2多相領域が拡大でき,広い組成範囲での組織制御が可能であると考えた。本年度は,Tiを2.5および5.0at%添加したCo-A1-Ni-Ti4元系B2/L1_2多相合金の組織形態と機械的性質の関係を調べた。 Ti添加量2.5,5.0at%の合金をアーク炉により溶製し,1373K,4h+1173K,24hの均質化熱処理を施した。組織および平衡相を調べるため光学顕微鏡観察,X線回折,示差熱分析を行い,機械的性質を調べるために,硬さ試験,室温から1273Kの温度範囲で圧縮試験を行った。その結果,2.5,5.0at%Ti両合金ともに組織はB2/(Co,Ni)2相,B2/L1_22相,B2/(Co,Ni)/L1_23相と思われる3つのタイプに大別できた。ほぼB2単相のB2/(Co,Ni)2相合金を除く全ての合金で4〜10%の圧縮塑性歪が得られ,L1_22相を含む合金では特に良好な室温延性が達成できた。全ての合金が室温で1000MPa以上の高強度を示し,0.2%変形応力(降伏強度)の温度依存性には,支配的である構成相の特徴が反映されることがわかった。例えば,B2相を多く含む合金では600から800Kの温度域で温度上昇に伴う強度低下が抑制されるB2型特有の温度依存性を示し,また,L1_2相を多量に含む合金ではL1_2相に起因する強度の正の温度依存性の発現によって600から800Kの温度域が最大強度を示した。Ti添加量が強度に与える影響はB2/L1_2相合金で顕著に現れ,Ti添加量を増加させると1073Kまでの温度域で200MPa程度の強度上昇が認められた。すなわち,Co-A1-Ni3元系からCo-A1-Ni-Ti4元系に拡張することでB2/L1_2多相領域がCo高濃度側に拡大でき,良好な延性,高強度を実現できた。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 1989 -1991 
    Author : SUZUKI Tomoo, YOSHIMURA Masahiro, MIURA Seiji, MISHIMA Yoshinao
     
    The research works which are regarding with rapid solidification of some intermetalic compounds can be summarized as follows ; (1) From the observations for microstructures of rapidly solidified TiAl alloys, informations for phase boundaries among alpha titanium, Ti_3Al and TiAl in the titanium-aluminum binary equilibrium phase diagram which have not been established were estimated. (2) From the results of systematic investigation for the effect of ternary elements on the tendency of metastable phases appearance in rapidly solidified Ni_3Al alloys, it was revealed that additional elements which inhibit the appearance of meta-stable phases have effects of improving the plasticity of Ni_3Al alloys. Although it was not apparent the relationships between these two phenomena, this results would give an effective way of improvement for the lack of plasticity that is considered as a neck for application of interm etallic compounds to structural materials.
  • Experimental study of alloy phase diagrams
    Date (from‐to) : 1991
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1990 -1990 
    Author : 三浦 誠司
  • 日本学術振興会：科学研究費助成事業
    Date (from‐to) : 1988 -1988 
    Author : 三浦 誠司

Industrial Property Rights

  • 特開2017-146294:圧子透過式試験体表面観察装置、観察方法及び動画像解析・装置制御・特性値演算用プログラム  2017/08/24
    宮島達也, 三浦誠司, 峯田才寛  立研究開発法人産業技術総合研究所／国立大学法人北海道大学
  • 特願2014-043677:擬弾性を示すマグネシウム合金、並びに擬弾性を示すマグネシウム合金部品およびその製造法  2016年/04/08
    鷲尾宏太, 三浦誠司
  • 特許5854497:Nb-Si系耐熱合金    2015/12/18
    三浦誠司, 毛利哲夫  国立大学法人 北海道大学
  • 特願PCT/JP2012/078683:ケイ化ニオブ基複合材並びにこれを用いたガスタービン用タービン動翼、ガスタービン用タービン静翼及び高温部品並びに当該高温部品を用いたガスタービン、ジェットエンジン及び高温熱機関  2012年/11/06
    三浦 誠司, 王 玉艇, 吉成 明
  • 特許5077943:PtTi系高温形状記憶合金    2012/09/07
    御手洗容子, 原 徹, 細田秀樹, 三浦誠司  独立行政法人物質・材料研究機構  
    特開２００８−１５０７０５
  • 特許4759748:試料膨張・収縮量計測システムおよび試料膨張・収縮量計測方法    2011/06/17
    三浦誠司, 岡 和彦, 毛利哲夫, 大久保賢二
  • 特願2011-508252:Cu−Al−Co系合金の電極・配線を具備した電子部品及びCu−Al−Co系合金の電極・配線用材料ならびにそれを用いた電極・配線用ペースト材料  2010年/04/08
    加藤 隆彦, 内藤 孝, 山本 浩貴, 青柳 拓也, 渡辺 精一, 三浦 誠司, 坂口 紀史, 青島 一貴, 大久保 賢二  
    WO/2010/116746
  • 特開2007-277613:細孔を有する金多孔質体およびその製造法  2007/10/25
    三浦誠司, 渡辺精一, 須田孝徳, 毛利哲夫, 大久保賢二  国立大学法人 北海道大学
  • 特開2006-241484:新規ニオブ基複合体及びその利用  2006/09/14
  • 特開2006-210434:酸化物半導体、酸化物半導体の製造方法、変位センサ  2006/08/10
    三浦誠司, 毛利哲夫, 大久保賢二
  • 特開2004-162178:Ir添加PtTi高温形状記憶合金  2004/06/10
    御手洗容子, 原 徹, 細田秀樹, 三浦誠司
  • 特開2002-105575:塑性加工用マグネシウム基合金複合材料および塑性加工用薄板材料の製造方法  2002/04/10
    三浦誠司, 毛利哲夫, 大久保賢二  北海道ティー・エル・オー株式会社

Social Contribution

  • ＳＳＨ運営指導委員
    Date (from-to) : 2015/05-Today
    Role : Organizing member
    Sponser, Organizer, Publisher  : 北海道室蘭栄高等学校
  • スーパーサイエンスハイスクールでの講義
    Date (from-to) : 2011-Today
    Role : Lecturer
    Sponser, Organizer, Publisher  : 北海道札幌啓成高等学校

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