萩原 幸司 (ハギハラ コウジ)

HAGIHARA Koji

写真a

所属学科・専攻等

物理工学教育類 材料機能分野
物理工学専攻 材料機能分野

職名

教授

メールアドレス

メールアドレス

ホームページ

http://hagihara.web.nitech.ac.jp

出身大学

  •  
    -
    2002年

    大阪大学   工学研究科   卒業

  •  
    -
    1997年

    大阪大学   工学部   卒業

出身大学院

  •  
    -
    2002年

    大阪大学  工学研究科  博士課程  修了

  •  
    -
    1997年

    大阪大学  工学部  博士課程  修了

取得学位

  • 大阪大学 -  博士(工学)

学外略歴

  • 2021年07月
    -
    継続中

      大阪大学   大学院工学研究科 マテリアル生産科学専攻   教授

  • 2021年04月
    -
    2021年06月

      大阪大学   大学院工学研究科 マテリアル生産科学専攻   教授

所属学会・委員会

  •  
     
     

    日本機械学会

  •  
     
     

    軽金属学会

  •  
     
     

    日本バイオマテリアル学会

  •  
     
     

    日本マグネシウム協会

  •  
     
     

    日本金属学会

全件表示 >>

 

論文

  • Comparison of microstructure, crystallographic texture, and mechanical properties in Ti–15Mo–5Zr–3Al alloys fabricated via electron and laser beam powder bed fusion technologies

    S.-H. Sun, K. Hagihara, T. Ishimoto, R. Suganuma, Y.-F. Xue, T. Nakano

    Additive Manufacturing ( Elsevier BV )  47   102329   2021年10月  [査読有り]

    研究論文(学術雑誌)   共著

    Depending on the application, establishing a strategy for selecting the type of powder bed fusion technology—
    from electron beam (EB-PBF) or laser powder bed fusion (L-PBF)—is important. In this study, we
    focused on the β-type Ti–15Mo–5Zr–3Al alloy (expected for hard-tissue implant applications) as a model material,
    and we examined the variations in the microstructure, crystallographic texture, and resultant mechanical
    properties of specimens fabricated by L-PBF and EB-PBF. Because the melting mode transforms from the conduction
    mode to the keyhole mode with an increase in the energy density in L-PBF, the relative density of the LPBF-
    built specimen decreases at higher energy densities, unlike that of the EB-PBF-built specimen. Although both
    EB-PBF and L-PBF can obtain cubic crystallographic textures via bidirectional scanning with a 90◦ rotation in
    each layer, the formation mechanisms of the textures were found to be different. The <100> texture in the build
    direction is mainly derived from the vertically grown columnar cells in EB-PBF, whereas it is derived from the
    vertically and horizontally grown columnar cells in L-PBF. Consequently, different textures were developed via
    bidirectional scanning without rotation in each layer: the <110> and <100> aligned textures along the build
    direction in L-PBF and EB-PBF, respectively. The L-PBF-built specimen exhibited considerably better ductility,
    but slightly lower strength than the EB-PBF-built specimen, under the conditions of the same crystallographic
    texture and relative density. We attributed this to the variation in the microstructures of the specimens; the
    formation of the α-phase was completely absent in the L-PBF-built specimen. The results demonstrate the
    importance of properly selecting the two technologies according to the material and its application.

  • Quantitative estimation of kink-band strengthening in an Mg–Zn–Y single crystal with LPSO nanoplates

    K. Hagihara, R. Ueyama, T. Tokunaga, M. Yamasaki, Y. Kawamura, T. Nakano

    Materials Research Letters ( Taylor and Francis )  9   467 - 474   2021年09月  [査読有り]

    研究論文(学術雑誌)   共著

    Kink-band strengthening was first quantitatively evaluated using an Mg–Zn–Y single crystal containing
    long-period stacking ordered (LPSO) nanoplates. The ability of a kink-band boundary to act
    as a barrier that hinders the motion of dislocations is high and comparable to that of a general random
    grain boundary. Nevertheless, a kink-band boundary is regarded as a simple tilt boundary in
    the dislocation model. One reason for the anomalous ability of kink-band boundary acting as barriers
    is related to its peculiar hierarchical structure, in which many small kink bands with high crystal
    rotation angles accumulate in a localized region.

  • Control of kink-band formation in mille-feuille structured Al/Al2Cu eutectic alloys

    K. Hagihara, T. Tokunaga, K. Nishiura, S. Uemichi, S. Ohsawa

    Materials Science & Engineering A ( Elsevier BV )  825   141849   2021年08月  [査読有り]

    研究論文(学術雑誌)   共著

    Kink bands have recently received significant attention owing to their ability to increase the strength and
    ductility of some Mg alloys. In this study, we first demonstrated that it is also expected even in Al alloys, by
    controlling the morphology of the introduced kink bands. Several directionally solidified Al–Cu alloys, wherein
    an Al/Al2Cu eutectic lamellar microstructure developed, were focused, and the variations in deformation
    behavior with microstructure were examined. The alloys can be deformed at room temperature, and the yield
    stress exhibits strong anisotropy. A high yield stress appears when stress is applied parallel to the lamellar
    interface, accompanied by kink-band formation. The microstructure was found to play an important role in
    controlling kink-band formation and the resultant mechanical properties. Only a few large kink bands form in a
    eutectic alloy specimen with a full lamellar microstructure, which is accompanied by a lower yield stress. Thus,
    the kink band cannot be used positively in it. In hypoeutectic alloys in which primary Al grains coexist with the
    lamellar microstructure, however, significantly high yield stresses appear, which are accompanied by the homogeneous
    formation of small kink bands. The results demonstrate that microstructural control can vary the role
    of the deformation kink band from the fracture (buckling) mode to the deformation mode via the change in its
    morphology. This enables a large increase in yield stress while maintaining the ductility of the Al/Al2Cu eutectic
    alloy. The high yield stress is maintained at temperatures up to ~300 ◦C owing to the high thermal stability of
    the lamellar microstructure. These findings provide new ways to develop novel high-temperature high-strength
    Al alloys.

  • Intrinsic kink bands strengthening induced by several wrought-processes in Mg-Y-Zn alloys containing LPSO phase

    H. Somekawa, D. Ando, K. Hagihara, M. Yamasaki, Y. Kawamura

    Materials Characterization ( Elsevier BV )  825   141849   2021年08月  [査読有り]

    研究論文(学術雑誌)   共著

    The kink bands strengthening effect was investigated using Mg-9at.%Y-6at.%Zn alloys produced by caliber
    rolling or extrusion at intermediate and elevated temperatures (373 K and more than 673 K). The results of
    microstructural observations showed that deformation kink bands were induced in all the alloys, regardless of
    the wrought-processing method and the processing temperatures. Micro-Vickers hardness tests showed that the
    regions including kink bands exhibited a higher hardness than those without kink bands, which reveal intrinsic
    kink bands strengthening. Interestingly, the trend of this kink bands strengthening effect could be expressed by
    an empirical relationship, which was divided into two lines associated with the wrought-processing temperature.
    This tendency did not appear to depend on the wrought-processing method. The alloys produced at the intermediate
    temperature showed markedly superior hardness, since, in addition to the kink bands strengthening, the
    residual strains/dislocations around kink boundaries contributed to obstruct dislocation slips.

  • Factor which governs the feature of texture developed during additive manufacturing; clarified from the study on hexagonal C40-NbSi2

    K. Hagihara, T. Ishimoto, M. Suzuki, R. Ozasa, A. Matsugaki, P. Wang, T. Nakano

    Scripta materialia ( Elsevier BV )  203   114111   2021年07月  [査読有り]

    研究論文(学術雑誌)   共著

    C40-NbSi 2 with a hexagonal unit cell is focused as a high-temperature structural material. We first at- tempted the fabrication of the bulk C40-NbSi 2 products via selective laser melting (SLM) in additive manufacturing (AM) process. Strong crystallographic texture control wherein < 0 0 01 > was parallel to the building direction, i.e. development of the so-called basal fiber texture, was achieved in this study. The texture developed in products does not largely vary by changing the scanning strategy, unlike the tex- tures of C11 b -MoSi2 with a tetragonal unit cell and a β-Ti alloy with a cubic unit cell. A comparison of these results led us to the conclusion that crystal symmetry, i.e., the multiplicity of the preferential crys- tal growth direction, is one of the primary factors that governs the features of the textures developed in AM-built materials.

  • Ultrahigh specific strength in a magnesium alloy strengthened by spinodal decomposition

    Tongzheng Xin, Yuhong Zhao, Reza Mahjoub, Jiaxi Jiang, Apurv Yadav, Keita Nomoto, Ranming Niu, Song Tang, Fan Ji, Zakaria Quadir, David Miskovic, John Daniels, Wanqiang Xu, Xiaozhou Liao, Long-Qing Chen, Koji Hagihara, Xiaoyan Li, Simon Ringer, Michael Ferry

    Science Advances ( American Association for the Advancement of Science (AAAS) )  7 ( 23 ) eabf3039 - eabf3039   2021年06月  [査読有り]

    研究論文(学術雑誌)   共著

    Strengthening of magnesium (Mg) is known to occur through dislocation accumulation, grain refinement, deformation twinning, and texture control or dislocation pinning by solute atoms or nano-sized precipitates. These modes generate yield strengths comparable to other engineering alloys such as certain grades of aluminum but below that of high-strength aluminum and titanium alloys and steels. Here, we report a spinodal strengthened ultralightweight Mg alloy with specific yield strengths surpassing almost every other engineering alloy. We provide compelling morphological, chemical, structural, and thermodynamic evidence for the spinodal decomposition and show that the lattice mismatch at the diffuse transition region between the spinodal zones and matrix is the dominating factor for enhancing yield strength in this class of alloy.

  • Formation of <0001>-rotation-type kink boundary in Mg–Zn–Y alloy with long-period stacking ordered structure

    Michiaki Yamasaki, Tsuyoshi Mayama, Tsubasa Matsumoto, Koji Hagihara, Daria Drozdenko, Yoshihito Kawamura

    Materials Science and Engineering: A ( Elsevier BV )  819   141466 - 141466   2021年05月  [査読有り]

    研究論文(学術雑誌)   共著

  • Stability of crystallographic texture in laser powder bed fusion: Understanding the competition of crystal growth using a single crystalline seed

    Takuya Ishimoto, Koji Hagihara, Kenta Hisamoto, Takayoshi Nakano

    Additive Manufacturing ( Elsevier BV )  43   102004 - 102004   2021年05月  [査読有り]

    研究論文(学術雑誌)   共著

  • Kink-band formation in directionally solidified Mg/Mg2Yb and Mg/Mg2Ca eutectic alloys with Mg/Laves-phase lamellar microstructure

    Koji Hagihara, Kosuke Miyoshi

    Journal of Magnesium and Alloys ( Elsevier BV )  in press   2021年04月  [査読有り]

    研究論文(学術雑誌)   共著

  • Surprising increase in yield stress of Mg single crystal using long-period stacking ordered nanoplates

    Koji Hagihara, Ryohei Ueyama, Michiaki Yamasaki, Yoshihito Kawamura, Takayoshi Nakano

    Acta Materialia ( Elsevier BV )  209 - 116797   2021年04月  [査読有り]

    研究論文(学術雑誌)   共著

全件表示 >>

著書

総説・解説記事

  • 計算,実験によるMg基LPSO相におけるキンク帯形成挙動の考察

    上山 椋平, 萩原 幸司, 眞山 剛, 山崎 倫昭, 河村 能人, 中野 貴由

    日本金属学会2019年(第165回)秋期講演大会講演概要集     2019年09月

    研究発表要旨(全国大会,その他学術会議)   共著

  • Mg基LPSO相におけるキンク帯形成・分布制御

    成本 裕希, 萩原 幸司, 中野 貴由, 山崎 倫昭, 河村 能人

    日本金属学会2019年(第165回)秋期講演大会講演概要集     2019年09月

    研究発表要旨(全国大会,その他学術会議)   共著

  • Mg-Zn-Y合金LPSO相における<0001>軸回転型キンク変形挙動

    山崎 倫昭, 中村 太亮, 萩原 幸司, ドロツデンコ ダリア, 井上 晋一, 河村 能人

    日本金属学会2019年(第165回)秋期講演大会講演概要集     2019年09月

    研究発表要旨(全国大会,その他学術会議)   共著

  • Mg-Zn-Y系18R-LPSO単相単結晶に形成されたキンク界面の転位構造

    松本翼, 山崎倫昭, 萩原幸司, 河村能人

    日本金属学会2018年(第163回)秋期講演大会講演概要集     2018年09月

    研究発表要旨(全国大会,その他学術会議)   共著

  • 六方晶系 Mg, Zn, MgZn2単結晶の溶解挙動の結晶方位依存性比較

    古田 智, 萩原 幸司, 中野 貴由, 山崎 倫昭

    日本金属学会2018年秋期講演(第163回)大会講演概要集     2018年09月

    研究発表要旨(全国大会,その他学術会議)   共著

  • キンク変形帯に着目したLPSO相押出合金の力学特性支配因子の検討

    萩原幸司, 李自宣, 山崎倫昭, 河村能人, 中野貴由

    日本金属学会2018年秋期講演(第163回)大会講演概要集     2018年09月

    研究発表要旨(全国大会,その他学術会議)   共著

科研費(文科省・学振)獲得実績

  • 力学コンフリクト組織制御による革新的「軽金属超合金」の創製

    挑戦的萌芽研究

    研究期間:  2021年07月  -  2023年03月  代表者:  萩原 幸司

  • 2500MPa超級超高機能過共析鋼の開発:強度・延性発現メカニズム解明

    基盤研究(B)

    研究期間:  2021年04月  -  2024年03月  代表者:  萩原 幸司

  • 骨異方性誘導のための「異方性の材料科学」の構築

    基盤研究(S)

    研究期間:  2018年06月  -  2023年03月  代表者:  中野貴由 (大阪大学)

  • ミルフィーユ構造の材料科学(研究に関する総括)

    新学術領域研究

    研究期間:  2018年06月  -  2023年03月  代表者:  阿部英司 (東京大学)

  • 力学解析によるキンク形成・強化のメカニズム解明

    新学術領域研究

    研究期間:  2018年06月  -  2023年03月  代表者:  萩原 幸司

受託研究受入実績

  • (公財)軽金属奨学会 研究助成

    提供機関:  

    研究期間: 2021年04月  -  2022年03月  代表者: 萩原 幸司

  • (公財)池谷科学技術振興財団 研究助成

    提供機関: 池谷財団 

    研究期間: 2021年04月  -  2022年03月  代表者: 萩原 幸司

  • JST CREST 機能マルチモーダル制御の材料科学と材料創製

    提供機関: JST CREST  一般受託研究

    研究期間: 2020年10月  -  2026年03月  代表者: 萩原 幸司

 
 

学会・委員会等活動

  • 2021年07月
    -
    現在

    軽金属学会   研究委員会 委員

  • 2019年03月
    -
    現在

    軽金属学会   国際交流委員

  • 2017年04月
    -
    2019年03月

    軽金属学会   大会運営委員

  • 2015年04月
    -
    2021年03月

    軽金属学会   関西支部 幹事委員

  • 2014年04月
    -
    2019年03月

    日本金属学会   欧文誌査読委員

  • 2013年
    -
    現在

    日本金属学会   分科会委員(第5分科,第3分科)

  • 2009年04月
    -
    2013年03月

    日本金属学会   学会会報(まてりあ)編集委員