論文 - 萩原 幸司
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Dynamic recovery around deformation kink boundary of Mg-Y-Zn alloy with long-period stacking ordered structure 査読あり 国際誌
Michiaki Yamasaki, Tsubasa Matsumoto, Tsuyoshi Mayama, Hidetoshi Somekawa, Koji Hagihara, Soya Nishimoto, Yoshihito Kawamura
Materials Letters 377 2024年09月
記述言語：英語 掲載種別：研究論文（学術雑誌）
This study demonstrated the possibility of dynamic recovery by forming a kink boundary in the long-period stacking ordered phase of the Mg85Y9Zn6 (at%) alloy. The compressive deformation at 1 % strain on the double-notched directionally solidified specimen produced three regions; undeformed, deformed, and kink-deformed regions. A nanoindenter was applied to three different regions. The deformed region sufficiently far from the kink boundary exhibited a 26 % higher nanoindentation hardness than the undeformed region owing to work-hardening, whereas the hardness decreased when approaching the kink boundary. At 1 μm or less from the kink boundary, the magnitude of hardness recovered to the same level as the undeformed region. This observation implies a “recovery kink zone” because of the dynamic recovery associated with kink boundary formation.
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Effects of multimodal microstructure on fracture toughness and its anisotropy of LPSO-type extruded Mg-1Zn-2Y alloys 査読あり 国際誌
Soya Nishimoto, Taiga Yasuda, Koji Hagihara, Michiaki Yamasaki
Journal of Magnesium and Alloys 12 2952 - 2966 2024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：Elsevier BV
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High-temperature strength and kink-band formation in mille-feuille-structured Ti/FeTi eutectic alloys 査読あり 国際誌
Toko Tokunaga, Takuya Yonemura, Koji Hagihara
Materials Science and Engineering A 900 146505 - 146505 2024年04月
担当区分：最終著者, 責任著者 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 BV
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Effect of Rolling and Alloying Elements on the Impact Properties of Hypereutectoid Steels 査読あり 国際誌
Toko Tokunaga, Yoritoshi Minamino, Koji Yamamoto, Toshiyuki Sugimoto, Koji Hagihara
ISIJ International 64 ( 6 ) 1078 - 1088 2024年04月
担当区分：最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Iron and Steel Institute of Japan
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Creep deformation behavior and microstructure of α-Mg/long-period stacking ordered (LPSO) duplex Mg-Y-Zn alloy prepared by hot extrusion and heat treatment 査読あり 国際誌
Takahiro Mineta, Daisuke Takahashi, Wataru Bando, Hiroyuki Sato, Koji Hagihara, Michiaki Yamasaki
Materials Today Communications 39 108912 - 108912 2024年04月
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New kink-band formation mechanism discovered in Zn-Al alloy with mille-feuille microstructure 査読あり 国際誌
Koji Hagihara, Shuhei Ohsawa, Toko Tokunaga
Materials and Design 239 112767 - 112767 2024年02月
担当区分：筆頭著者, 責任著者 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 BV
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Stress-induced symmetrical tilt boundaries in layer-structured Al-Cu eutectic alloys 査読あり
Daisuke Egusa, Tsuyoshi Mayama, Koji Hagihara, Eiji Abe
Scripta Materialia 244 116025 2024年02月
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Effects of cementite particles on impact properties in high-hardness hypereutectoid steels 査読あり
T. Tokunaga , K. Yamamoto , Y. Minamino , T. Takayama , T. Sugimoto , K. Hagihara
ISIJ International 64 389 - 400 2024年01月
担当区分：最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
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Local Plastic Deformation of Kink Band Opposing External Stress in Mg–Zn–Y Alloy 査読あり 国際誌
Ryutaro Matsumura, Yuri Ueda, Koji Hagihara, Yuri Shinohara, Tomonari Inamura
Materials Transactions 65 ( 1 ) 101 - 104 2024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：Japan Institute of Metals
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Contributions of multimodal microstructure in the deformation behavior of extruded Mg alloys containing LPSO phase 査読あり 国際誌
Koji Hagihara, Tsuyoshi Mayama, Michiaki Yamasaki, Stefanus Harjo, Toko Tokunaga, Kazuki Yamamoto, Mika Sugita, Kairi Aoyama, Wu Gong, Soya Nishimoto
International Journal of Plasticity 173 103865 2023年12月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
The unique control mechanisms of the plastic deformation of two-phase extruded alloy composed of Mg and long-period stacking ordered (LPSO) phase were clarified by comparison with those of other Mg solid-solution alloys, focusing on the question “why do the Mg/LPSO two-phase alloys exhibit both large elongation and high strength?”. The stress-strain curves for each grain in the alloys could be imaginary estimated using neutron diffraction analysis during the tensile test. The results demonstrate that the deformation behaviors of the worked and recrystallized grains are significantly different in all the Mg-extruded alloys owing to the strong plastic anisotropy in Mg with hexagonal close-packed (hcp) structure. Therefore, the deformation behavior is controlled by a composite-like deformation mechanism, even in single-phase Mg solid-solution alloys. In Mg-Y-Zn ternary alloys, the recrystallized Mg grains exhibited significant lattice softening at the initial stage of yielding owing to the escape of basal dislocations from the Y/Zn dragging atmosphere. However, the worked grains acted as strengthening components. In the Mg/LPSO two-phase alloy, the composite-like deformation behavior was enhanced, and the LPSO phase significantly contributed to the strengthening of the alloy. Moreover, it was hypothesized that the LPSO phase contributes not only to the alloy's strength but also to its elongation by increasing the work-hardening rate. We proposed the new concept “Anisotropic Mechanical property-Induced Ductilization (AMID)” by multimodal microstructure, to explain this phenomenon. As the physical origin for inducing AMID, kink-band strengthening in the LPSO phase is believed to be one of the reasons for the increase in the work-hardening rate of the extruded LPSO-phase grains in the Mg/LPSO two-phase alloy, resulting in an improved ductility.
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Verifcation of Rank-1 Connection Model of Kink Band in Mg–Zn–Y Alloy 査読あり
Ryutaro Matsumura, Koji Hagihara, Tomonari Inamura
Materials Transactions 65 97 - 100 2023年11月
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Modification of grain boundary microstructure by controlling dissolution behavior of θ particles in Cr-containing hypereutectoid steel 査読あり
Koji Yamamoto , Takemori Takayama , Yoritoshi Minamino , Yuichiro Koizumi , Toko Tokunaga , Koji Hagihara
Materials Characterization 205 113241 2023年10月
担当区分：最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
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Development of Zn–Mg–Ca Biodegradable Dual-Phase Alloys 査読あり
Koji Hagihara , Shuhei Shakudo , Toko Tokunaga , Takayoshi Nakano
Metals 13 ( 6 ) 1 - 13 2023年06月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
DOI： 10.3390/met1306109
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Investigation of the electronic structure of the Mg99.2Zn0.2Y0.6 alloy using X-ray photoelectron spectroscopy 査読あり
Hidetoshi Miyazaki , Tatsuyoshi Akatsuka , Koji Kimura , Daisuke Egusa , Yohei K. Sato , Mitsuhiro Itakura , Yasumasa Takagi , Akira Yasui , Kenichi Ozawa , Kazuhiko Mase , Toko Tokunaga , Kouichi Hayashi , Koji Hagihara , Eiji Abe
Materials Transactions 64 1194 - 1198 2023年06月
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Effect of short-range order on the high-temperature plastic deformation behavior of Ni–Cr–W, Ni–W, and Ni–Re single crystals 査読あり
Koji Hagihara
Journal of Materials Science and Technology 165 143 - 152 2023年05月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
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Local structural analysis around solute-element in annealed Mg99.2Zn0.2Y0.6 alloy using X-ray fluorescence holography 査読あり
Koji Kimura , Daisuke Egusa , Koji Hagihara , Naohisa Happo , Naomi Kawamura , Hiroo Tajiri , Kouichi Hayashi , Eiji Abe
Materials Transactions 64 750 - 755 2023年04月
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Synchronized Formation of Kink Bands in Al/Al2Cu Mille-Feuille Structured Alloy 査読あり
Takayuki Shiraiwa , Naoya Hamada , Fabien Briffod , Manabu Enoki , Koji Hagihara
Materials Transactions 64 735 - 743 2023年04月
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Relationship between Cluster-Arranged Nanoplate Formation and Mechanical Properties of Dilute Mg–Y–Zn Alloys Prepared by Combination of Low-Cooling-Rate Solidification and Extrusion Techniques 査読あり
Seitaro Ishizaki , Michiaki Yamasaki , Koji Hagihara , Soya Nishimoto , Taisuke Nakamura , Yoshihito Kawamura
Materials Transactions 64 756 - 765 2023年04月
記述言語：英語 掲載種別：研究論文（学術雑誌）
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Unified Understanding of Strengthening Mechanisms Acting in Mg/LPSO Two-Phase Extruded Alloys with Varying LPSO Phase Volume Fraction 査読あり
Koji Hagihara , Toko Tokunaga , Kazuki Yamamoto , Michiaki Yamasaki , Tsuyoshi Mayama , Takumi Shioyama , Yoshihito Kawamura , Takayoshi Nakano
Materials Transactions 64 720 - 729 2023年04月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌）
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Impact of gas flow direction on the crystallographic texture evolution in laser beam powder bed fusion 査読あり 国際共著
Hiroki Amano , Takuya Ishimoto , Koji Hagihara , Ryoya Suganuma , Keisuke Aiba , Shi-Hai Sun , Pan Wang , Takayoshi Nakano
Virtual and Physical Prototyping 18 2023年02月
記述言語：英語 掲載種別：研究論文（学術雑誌）
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