論文 - 萩原 幸司
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OS0316 Mg_<12>ZnY長周期相の塑性変形機構,Mg合金強化機構(非立方晶型金属材料の変形現象とそのモデル化,オーガナイズドセッション)
萩原 幸司, 木下 昭人, 山崎 倫昭, 河村 能人, 馬越 祐吉
M&M材料力学カンファレンス 2009 ( 0 ) 732 - 733 2009年
記述言語：日本語 掲載種別：研究論文（学術雑誌） 出版者・発行元：一般社団法人 日本機械学会
Recently, the role of the strengthening phase with a long-period stacking ordered (LPSO) structure is focused for development of high-strength Mg alloys. In this study, the plastic deformation behavior of Mg_<12>ZnY with 18R LPSO-stnicture was investigated and the strengthening mechanism of the Mg/LPSO two-phase alloys was discussed. The (0001)<1120> basal slip was identified to be the dominant operative deformation mode in the LPSO phase, and deformation kinks were initiated to accommodated the compressive strain. The results showed that the plastic behavior of LPSO-phase is highly anisotropic. The existence of LPSO-phase in Mg alloys induces the grain refmement of Mg matrix grains dunng extrusion. In addition, it effectively acts as a fiber-like strengthening phase in deformation along the extruded direction.
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Role of the Microstructure on the Deformation Behavior in Mg12ZnY With a Long-Period Stacking Ordered Structure 査読あり
K. Hagihara, N. Yokotani, A. Kinoshita, Y. Sugino, H. Yamamoto, M. Yamasaki, Y. Kawamura, Y. Umakoshi
ADVANCED INTERMETALLIC-BASED ALLOYS FOR EXTREME ENVIRONMENT AND ENERGY APPLICATIONS 1128 329 - + 2009年
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：MATERIALS RESEARCH SOC
The influence of a heat-treatment on the plastic deformation behavior in Mg12ZnY with a long-period stacking ordered (LPSO) structure was investigated by using crystals grown by the Bridgman method. Annealing of the crystal at 798 K for 3 days induced the change in the crystal structure of Mg12ZnY from the 18-fold rhombohedral structure (18R) to the 14-fold hexagonal structure (14H). The plastic behavior of those LPSO crystals showed a large variation depending on the loading axis in both crystals, because of the limitation of operative deformation modes in them. The change in the stacking sequence in the LPSO crystals did not show a large influence on the plastic deformation behavior at room temperature.
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Influence of heat-treatment on microstructure and plastic deformation behavior in Ni3V single crystals with the D022 structure 査読あり
K. Hagihara, M. Mori, T. Kishimoto, Y. Umakoshi
Journal of Physics: Conference Series 165 12004 2009年
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：Institute of Physics Publishing
The control of microstructure in Ni3V single crystals such as variant and anti-phase boundary (APD) was attempted by quenching from the disordered state followed by annealing at several temperatures. In the heat-treatments, the microstructure strongly varied depending on the quenching speed from the disordered state. In slow-quenching, the lamellar structure composed of two variants was developed after annealing, as reported in many polycrystalline samples. However, only one of three variants was preferentially grown in the specimen rapidly quenched from the disordered state followed by annealing. The yield stress of slow-quenched specimen showed more than twice the value of the fast-quenched specimen. © 2009 IOP Publishing Ltd.
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Single-crystal growth and plastic deformation behaviour of a Ti-15Mo-5Zr-3Al alloy for biomedical application 査読あり
S. H. Lee, K. Hagihara, M. H. Oh, T. Nakano
Journal of Physics: Conference Series 165 12086 2009年
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：Institute of Physics Publishing
A Ti-15Mo-5Zr-3Al alloy with a bcc structure are promising materials for biomedical application and were examined. The focus of this study was on the effect of heat treatment on microstructure and plastic deformation behaviour using a single crystal. The single crystal was successfully obtained by a floating zone method at a crystal growth rate of 2.5 mm/h. A slip at the <
111>
dislocation was present irrespective of heat treatment at 573K or 673K for 1.2 ks or 300 ks. The yield stress at the [149] loading axis varied significantly depending on microstructure, especially from the precipitation of the a phase. Al addition suppresses generation of the σ phase and increases the yield stress at the same time. © 2009 IOP Publishing Ltd. -
極低酸素分圧雰囲気下でのTi単結晶の帯溶融育成 査読あり
萩原幸司, 橘 孝洋, 佐々木啓太, 吉田良行白川直樹, 長澤 亨, 成島尚之, 中野貴由
日本金属学会誌 72 ( 12 ) 928 - 934 2008年12月
記述言語：日本語 掲載種別：研究論文（学術雑誌）
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Peculiar elastic behavior of Ti-Nb-Ta-Zr single crystals 査読あり
M. Tane, S. Akita, T. Nakano, K. Hagihara, Y. Umakoshi, M. Niinomi, H. Nakajima
ACTA MATERIALIA 56 ( 12 ) 2856 - 2863 2008年07月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD
The cause of a low Young's modulus was investigated in quaternary P-type Ti-Nb-Ta-Zr alloys, as the modulus is decreased to prevent bone absorption and degradation of bone quality when these alloys are implanted into human bones. This investigation was carried out using the alloys' single crystals. Acoustic measurements and analysis by the Hill approximation revealed that a low Young's modulus in a polycrystalline form is caused by the low shear modulus c', related to the low P-phase stability, low c(44), and relatively low bulk modulus B compared with those of binary Ti-based alloys. Furthermore, it was found that the single crystals had strong orientation dependence on Young"s modulus, where that in the < 100 >-direction E-100 is the lowest of all crystallographic orientations. For quaternary Ti29Nb-13Ta-4.6Zr alloy (mass%), E-100 is only similar to 35 GPa, which is similar to Young's modulus of human cortical bones as a result of the low B and c'. These results indicate that decreases in c', c(44) and B are essential for decreasing Young's modulus of novel beta-type Ti alloys which are expected to be developed in the near future. (c) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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長周期積層構造相の力学特性、塑性変形挙動 招待あり
萩原幸司
日本金属学会分科会シンポジウム「長周期積層構造型マグネシウム合金の現状と今後の課題」 予稿 29 - 32 2008年05月
記述言語：日本語 掲載種別：研究論文（学術雑誌）
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Fabrication and Plastic Deformation Behavior of Lamellar Ti-rich TiAl Crystals with Lotus-Type Aligned Pores 査読あり
T. Nakano, T. Tachibana, K. Hagihara, Y. Umakoshi, T. Ide, M. Tane, H. Nakajima
POROUS METALS AND METALLIC FOAMS: METFOAM 2007 213 - + 2008年
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：DESTECH PUBLICATIONS, INC
Ti-rich TiAl crystals are a promising candidate as light-weight and heat-resistant materials for aerospace and automobile applications.
In this study, we fabricated Ti-48.0at.%Al (Ti-rich TiAl) crystals with lotus-type aligned pores, and examined the microstructure and plastic deformation behavior. We succeeded in obtaining the gamma/alpha(2) two-phase lamellar Ti-rich TiAl crystals with elongated pores aligned parallel to the heat transfer direction by the floating zone method under the pressure of hydrogen and helium mixed gas at a crystal growth :ate of 330 mu m/s. The as-grown and annealed crystals show a well-developed lamellar structure with a strict orientation relationship between the alpha(2) phase and six gamma variants in each grain. However, these crystals exhibit no strong texture of lamellar grains. The total pore volume and the mean pore diameter are approximately 52 % and 380 pm, respectively.
The macro-yield stress strongly depends on the loading axis relative to the elongated pore. When the loading axis is parallel and perpendicular to the elongated pore direction, the yield stress obeys K=1 and 2.5, respectively, in the equation of sigma=sigma(0)(1-P)(kappa), where a is the macro-yield stress with pores, sigma(0) is the macro-yield stress without pores and P is the volume fraction of pores. The difference of K value, K=1 and 2.5, indicates the change in deformation manner, i.e. macroscopically homogeneous and locally heterogeneous plastic deformation, respectively. The plastic deformation behavior was also investigated at elevated temperatures up to 1273 K. The relatively high stress was maintained independent of the loading axis up to around 1073 K. The K value shows no strong temperature dependence because aligned pores give no change in deformation behavior at elevated temperatures. -
Crystal growth and plastic deformation behavior of Ti-29Nb-13Ta-4.6Zr bcc-based single crystal 査読あり
T. Nakano, K. Hagihara, H. Maki, Y. Umakoshi, M. Niinomi
Proc. Ti-2007 JIMIC5 (Science and Technnology) 1437 - 1439 2007年06月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
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Effect of bcc-phase stability on cyclic deformation behavior in beta-type Ti-Nb-Ta-Zr alloys single crystals with different Nb content 査読あり
K. Hagihara, T. Nakano, A. Sonoura, K. Watanabe, Y. Umakoshi, M. Niinomi
Proc. in Ti-2007 1445 - 1447 2007年06月
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス）
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Effect of C11(b)-Stabilized element on deformation mode in C40-type (Nb1-xMox)Si-2 (x=0-0.85) single crystals
Takayoshi Nakano, Koji Hagihara, Yukichi Umakoshi
ADVANCED INTERMETALLIC-BASED ALLOYS 980 297 - + 2007年
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：MATERIALS RESEARCH SOC
Plastic deformation behavior and the dominant deformation mode in ternary (Nb1-xMox)Si-2 (x=0-0.85) single crystals with the C40 structure were examined focusing on the phase stability between the C40 and C11(b) structures. Temperature dependence of CRSS for the (0001) < 2 (1) over bar(1) over bar0] slip is strongly influenced by the Mo concentration accompanied by the change in the dissociation mode from the co-planar-type to the synchroshear-type. In the ternary crystals with x=0-0.30, anomalous strengthening clearly appeared, and the peak stress increased up to 1600 degrees C with an increase in the Mo content. Mo atoms may gather and form a dragging atmosphere around 1/3 < 2 (1) over bar (1) over bar 0] dislocations containing a superlattice intrinsic stacking fault (SISF), resulting in anomalous strengthening. In contrast, in crystals with x=0.60-0.85, a high CRSS was obtained with fracture in a brittle manner at low temperatures, and the stress decreased remarkably with an increase in the test temperature. HRTEM observation showed that the synchroshear-type dissociation of each super-partial dislocation, 1/6 < 2 (1) over bar (1) over bar 0], occurred on the neighboring slip planes, accompanied by a much wider separation distance of SF than that in the ternary crystals with a low Mo content. This change in plastic deformation behavior may be closely related to the decrease in phase stability of the C40 structure with the addition of the C11(b)-stabilized element, Mo. The phase stability can be represented by the ratio of h/b, where h is the (0003) spacing and b is the amplitude of 1/3 < 2 (1) over bar (1) over bar 0 As the h/b ratio increases with the addition of Mo, the dissociation mode chances from the co-planar-type to the synchroshear-type at a ratio of 0.465.
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Microstructure and plastic deformation behavior of Ni3V single crystals 査読あり
Koji Hagihara, Mayumi Mori, Yukichi Umakoshi
PRICM 6: SIXTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, PTS 1-3 561-565 407 - + 2007年
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：TRANS TECH PUBLICATIONS LTD
Plastic deformation behavior of Ni3V with D0(22) structure was examined using the single crystals containing two dominant variants of three. At [557] loading orientation, {111} 1/6 < 112] twinning is dominantly operative at low temperatures, but {111} 1/2 < 112] slip is activated at high temperatures accompanied by a rapid drop of yield stress.
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Microstructure and deformation behavior of lamellar Ti-rich TiAl crystal with lotus-type aligned pores 査読あり
Takayoshi Nakano, Takahiro Tachibana, Koji Hagihara, Yukichi Umakoshi, Takuya Ide, Masakazu Tane, Hideo Nakajima
PRICM 6: SIXTH PACIFIC RIM INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS AND PROCESSING, PTS 1-3 561-565 383 - + 2007年
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：TRANS TECH PUBLICATIONS LTD
A porous Ti-48.0at.%Al (Ti-rich TiAl) crystal, in which lotus-type long cylindrical pores were aligned and (gamma/alpha(2)) two-phase lamellar structure was simultaneously developed, was fabricated by floating zone method under the pressure of hydrogen and helium mixed gas. Plastic deformation behavior and microstructure of the Ti-rich TiAl crystal with lotus-type aligned pores were investigated by focusing on the elongated pore direction. The as-grown and annealed crystals show a well-developed lamellar structure and no texture accompanied by 52% porosity and a mean pore diameter of 380 mu m. Yield stress strongly depends on the loading direction against the elongated pore. When loading directions are parallel and perpendicular to the pore direction, yield stresses obey K=1 and 2.5, respectively, in equation of sigma=sigma(0)(1-P)(K), where a is the yield stress with pores, sigma(0) is the yield stress without pores and p is porosity. This reflects macroscopically homogeneous and locally heterogeneous plastic deformation between pores, respectively.
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Plastic deformation behavior of oriented Ni3V crystals with D0(22) structure 査読あり
Koji Hagihara, Mayumi Mori, Yukichi Umakoshi
ADVANCED INTERMETALLIC-BASED ALLOYS 980 523 - + 2007年
記述言語：英語 掲載種別：研究論文（国際会議プロシーディングス） 出版者・発行元：MATERIALS RESEARCH SOC
Plastic deformation behaviour of Ni3V with D0(22) structure was examined using the single crystals containing two dominant variants of three. Three deformation modes were confirmed to be operative depending on temperature and loading orientation. {111} 1/6 < 112] twinnng and/or {111} < 110] slip isa dominantly operative at low temperatures, but {111} 1/2 112] slip is activated at high temperatures accompanied by a rapid of yield stress.
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Effects of the anisotropy of the anti-phase boundary energy on the yield-stress anomaly in Ni3X compounds with close-packed crystal structures 査読あり
K. Hagihara, T. Tanaka, T. Nakano, P. Veyssiere, Y. Umakoshi
PHILOSOPHICAL MAGAZINE LETTERS 87 ( 10 ) 705 - 712 2007年
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：TAYLOR & FRANCIS LTD
This paper is aimed at clarifying the effects of the anisotropy of the anti-phase boundary (APB) energy on the yield-stress anomaly (YSA) of five distinct Ni-3(Ti, Nb) single crystals with various long-period ordered structures, in which the APB energy on the non-close-packed (non-CP) plane varies with changes in the stacking sequence of the close-packed planes. The APB energies of interest are estimated, based on a pair-wise interaction parameter model to the second neighbour. The YSA can be categorized in two groups of two and three compounds, within which the mechanical properties are nearly independent of composition. The microstructures resulting from deformation at 700 degrees C were compared. It is verified that the YSA is dominantly controlled by differences in the probability of locking by a Kear-Wilsdorf mechanism, which itself is governed by the anisotropy of APB energy in the non-CP planes relative to the primary slip plane.
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Ni3X型金属間化合物の結晶構造と塑性変形挙動 招待あり 査読あり
萩原幸司
まてりあ 45 813 - 816 2006年11月
記述言語：日本語 掲載種別：研究論文（学術雑誌）
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Isothermal oxidation behavior of two-phase TiAl-Mn-Mo-C-Y alloys fabricated by different processes
Y Wu, SK Hwang, K Hagihara, Y Umakoshi
INTERMETALLICS 14 ( 1 ) 9 - 23 2006年01月
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER SCI LTD
The isothermal oxidation behavior of two-phase Ti-46.6Al-1.4Mn-2Mo-0.3C-0.3Y based alloys in synthetic air at 800 and 900 degrees C was investigated. The main emphasis was focused on the effect of microstructures obtained by different processes of extrusion, melting and hot rolling, i.e. fully lamellar, nearly lamellar and duplex. On the exposure for 350 h at 800 degrees C, the growth rate and the spallation behavior of oxide scales of the alloys depended strongly on the fabrication process. The extruded alloy with a fine fully lamellar microstructure showed an excellent oxidation resistance due to the lowest mass gain and strong adhesion of the scale to the substrate, and Y-addition was effective in improving oxidation resistance because of its oxygen-scavenging effect in EPM processing. However, the overall oxidation process was dominantly controlled by the beneficial effect of the Mo-addition in the melted alloy due to the doping effect and formation of Mo-rich Al-depletion layer close to the substrate. The rolled alloy with the duplex microstructure greatly accelerated the oxidation rate because of a high volume fraction of alpha(2)-Ti3Al. At 900 degrees C, the melted alloy showed an excellent oxidation resistance during 350 h exposure. The oxidation rate and the spallation resistance of oxide scales did not depend strongly on the microstructure for the extruded or the rolled alloy. The poor spallation resistance of the oxide scales in the extruded alloy was probably related to thicker Mn-containing scales. Neither Mo-rich layer nor Y-rich zone in the oxide scales in the rolled alloy was observed at two exposure temperatures as a result of fast oxidation rate of the scale. (c) 2005 Elsevier Ltd. All rights reserved.
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The effect of Ti-addition on plastic deformation and fracture behavior of directionally solidified NiAl/Cr(Mo) eutectic alloys
K. Hagihara, Y. Sugino, Y. Umakoshi
INTERMETALLICS 14 ( 10-11 ) 1326 - 1331 2006年
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER SCI LTD
To improve the high-temperature strength of NiAl/Cr(Mo) eutectic alloys, the effect of Ti-addition on microstructure and mechanical properties was examined. Three directionally solidified (DS) alloys with the composition of Ni-(33 - x)Al-31Cr-3Mo-xTi (x = 0, 3 and 5 at.%, respectively), denoted 0Ti-, 3Ti- and 5Ti-alloys hereafter, were prepared. Temperature dependence of the yield stress and the room temperature fracture toughness of these DS alloys was examined. The aligned lamellae with B2-NiAl and A2-Cr(Mo) were formed in 0Ti-alloy, but the formation of lamellar structure was hindered by the Ti-addition. Cellular microstructures containing short plate shapes of Cr(Mo) phases were obtained in 3Ti- and 5Ti-alloys. In 5Ti-alloy, the precipitation of the L2(1)-Ni2AlTi was continued in NiAl matrix phase after the DS treatment. The Ti-addition induced a significant increase in high-temperature strength accompanied by a large deterioration of room temperature fracture toughness. The fracture toughness of 5Ti-alloy showed the low value of about 4 MPa m(1/2) because of the disturbance of microstructure. (C) 2006 Elsevier Ltd. All rights reserved.
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骨再建のための骨代替材料のナノ解析と骨質評価 査読あり
中野貴由, 萩原幸司, 馬越佑吉, 明石満, 中嶋英雄, 今里聡, 田畑泰彦
日本金属学会2006 年春期（第138 回）大会（2006.3.21－23. 東京） 2006年
記述言語：日本語 掲載種別：研究論文（学術雑誌）
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Microstructure and plastic deformation behavior of Ni-3(Ti,X) (X = Nb,Al) single crystals with long-period geometrically closely packed crystal structures 査読あり
K. Hagihara, T. Tanaka, H. Fujimoto, T. Nakano, Y. Umakoshi
INTERMETALLICS 14 ( 10-11 ) 1332 - 1338 2006年
記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：ELSEVIER SCI LTD
The crystal structure, phase stability and plastic deformation behavior of Ni-3(Ti1-xNbx) [x = 0, 0.01, 0.03, 0.05 or 0.10] and Ni3(Ti1-yAly) [y = 0.16 or 0.28] single crystals were investigated. The Substitution of Ti by Nb in Ni3Ti induced the formation of various long-period stacking ordered (LPSO) structures with 18-fold, 10-fold or 9-fold stacking sequences of closely packed plane (CPP) depending on the Nb content. In compression tests, the yield stress anomaly (YSA) appeared in ternary LPSO crystals as well as in binary Ni3Ti by slip on the CPP. The change in stacking sequence of CPP in the LPSO phases strongly affects the YSA behavior due to the change in APB energy on the non-closely packed plane. (C) 2006 Elsevier Ltd. All rights reserved.
