Papers - HAGIHARA Koji
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Loading orientation dependence of the formation behavior of deformation kink bands in the Mg-based long-period stacking ordered (LPSO) phase Reviewed International journal
Koji Hagihara, Takuya Okamoto, Ryohei Ueyama, Michiaki Yamasaki, Yoshihito Kawamura, Takayoshi Nakano
Materials Transactions 61 ( 5 ) 1821 - 1827 2020.01
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
© 2019 The Japan Institute of Metals and Materials The variation in the deformation behavior of a directionally solidified (DS) Mg-based long-period stacking ordered (LPSO)-phase crystal depending on the loading orientation was examined. The frequency of formation of the beak-like shape of the deformation band, which is known as one of the important deformation mechanisms in the LPSO phase, monotonically decreased as the inclination angle of the loading orientation with respect to the crystal growth direction in the DS crystal increased, and was accompanied by a decrease in the yield stress due to the activation of basal slip. Deformation bands formed along a direction approximately perpendicular to the grain boundary independent of the loading orientation. The crystal rotation axes selected in the deformation bands were perpendicular to [0001] in almost all grains, independent of the loading orientation. However, the rotation axes in the bands were not fixed but varied between h1010 - i and h1120 - i; this variation was correlated with the loading axis. These observed features strongly suggest that the deformation bands formed in the LPSO phase are predominantly deformation kink bands and that the formation mechanism itself does not vary with the loading orientation but instead its details. The selectivity of the crystal rotation axis in the kink band is strongly affected by the loading orientation.
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Control of crystallographic orientation by metal additive manufacturing process of β-type Ti alloys based on the bone tissue anisotropy Invited Reviewed International journal
Takayoshi Nakano, Takuya Ishimoto, Aira Matsugaki, Koji Hagihara, Yuichiro Koizumi, Ryosuke Ozasa
MATEC Web of Conferences 321 05002 - 05002 2020
Language：English Publishing type：Research paper (scientific journal) Publisher：EDP Sciences
Variation in the scanning strategy for β-type Ti alloys during additive manufacturing (AM) enables the fabrication of a singlecrystal-like microstructure possessing a crystallographic texture, in which the low-Young’s modulus-<100> direction is aligned along a specific direction. Thus, metal biomaterial with low elasticity, comparable to the bone Young’s modulus, can be developed by AM, which will contribute to suppress the stress shielding of bone and prevent degradation of bone tissue anisotropy.
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Enhancement of plastic anisotropy and drastic increase in yield stress of Mg-Li single crystals by Al-addition followed by quenching Reviewed
K. Hagihara, K. Mori, T. Nakano
Scripta Materialia 2019.07
Language：English Publishing type：Research paper (scientific journal)
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Quantitative ultrasound (QUS) axial transmission method reflects anisotropy in micro-arrangement of apatite crystallites in human long bones: A study with 3-MHz-frequency ultrasound Reviewed
T. Ishimoto, R. Suetoshi, D. Cretin, K. Hagihara, J. Hashimoto, A. Kobayashi, T. Nakano
Bone 127 82 - 90 2019.07
Publishing type：Research paper (scientific journal)
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Fabrication of the beta-titanium alloy rods from a mixture of pure?metallic element powders via selected laser melting Reviewed
M. Todai, T. Nagase, T. Hori, H. Motoki, S.-H. Sun, K. Hagihara, T. Nakano
Materials Science Forum 941 1260 - 1263 2019.07
Publishing type：Research paper (scientific journal)
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Strengthening of Mg-based long-period stacking ordered (LPSO) phase with deformation kink bands Reviewed
K. Hagihara, M. Yamasaki, Y. Kawamura, T. Nakano
Materials Science & Engineering A 763 138163 2019.07
Publishing type：Research paper (scientific journal)
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Additive Manufacturing プロセスによるシリサイド金属間化合物の結晶方位・組織制御 Reviewed International journal
萩原幸司, 石本卓也, 孫世海, 中野貴由
スマートプロセス学会誌 8 84 - 89 2019.04
Language：English Publishing type：Research paper (scientific journal)
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Cr, Ir 共添加によるC40/C11b超高温耐熱複相シリサイドの格子ラメラ組織制御 Reviewed
萩原幸司, 池西貴昭, 中野貴由
日本金属学会誌まてりあ 58 81 2019.02
Language：Japanese Publishing type：Research paper (scientific journal)
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Mg 基LPSO 相をはじめとする種々の異方性材料に見られる特異な変形帯形成 Reviewed
萩原幸司, 中野貴由, 山崎倫昭, 河村能人
日本金属学会誌まてりあ 57 607 2018.11
Language：Japanese Publishing type：Research paper (scientific journal)
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Strengthening mechanisms acting in extruded Mg-based long-period stacking ordered (LPSO)-phase alloys Reviewed
K. Hagihara, Z.Li, M. Yamasaki, Y. Kawamura, T. Nakano
Acta Materialia 15 226 - 239 2018.10
Language：English Publishing type：Research paper (scientific journal)
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In-plane positional correlations among dopants in 10H type long period stacking ordered Mg75Zn10Y15 alloy studied by X-ray fluorescence holography Reviewed
T. Nishioka, Y. Yamamoto, K. Kimura, K. Hagihara, H. Izuno, N. Happo, S. Hosokawa, E. Abe, M. Suzuki, T. Matsushita, K. Hayashi
Materialia 3 256 - 259 2018.09
Language：English Publishing type：Research paper (scientific journal)
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Plastic deformation behavior and operative slip systems in Mg17Al12 single crystals Reviewed
K. Hagihara, K. Hayakawa
Materials Science & Engineering A 737 393 - 400 2018.09
Language：English Publishing type：Research paper (scientific journal)
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Excellent mechanical and corrosion properties of austenitic stainless steel with a unique crystallographic lamellar microstructure via selective laser melting Reviewed
S.-H. Sun, T. Ishimoto, K. Hagihara, Y. Tsutsumi, T. Hanawa, T. Nakano
Scripta Materialia 159 89 - 93 2018.09
Language：English Publishing type：Research paper (scientific journal)
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Configuration of dislocations in low-angle kink boundaries formed in a single crystalline long-period stacking ordered Mg-Zn-Y alloy Reviewed
Tsubasa Matsumoto, Michiaki Yamasaki, Koji Hagihara, Yoshihito Kawamura
Acta Materialia 151 112 - 124 2018.06
Language：English Publishing type：Research paper (scientific journal) Publisher：Acta Materialia Inc
The dislocation configuration around low-angle kink boundaries formed in bent single crystalline long-period stacking ordered (LPSO) Mg85Zn6Y9 alloys was investigated. Intragranular misorientation axis (IGMA) analysis through SEM/EBSD observation and g•b analysis through TEM observation were conducted. Various kink bands possessing different lattice rotation axes ranging from <
11¯00>
to <
12¯10>
i.e. along <
11¯00>
<
uvt0>
and <
12¯10>
were revealed using IGMA analysis. TEM observation with g•b analysis unveiled that the <
11¯00>
-rotation kink boundary observed using IGMA analysis consisted of basal <
a>
edge dislocations with one Burgers vector, while the <
12¯10>
/<
uvt0>
-rotation kink boundaries were comprised of basal <
a>
edge dislocations with more than one Burgers vector. Low-angle kink boundaries were regarded as low-angle tilt boundaries consisting of perfect basal <
a>
dislocations, regardless of their rotation axes. The formation of various kink bands with <
uvt0>
-combination-rotation axes ranging from <
11¯00>
to <
12¯10>
suggests that the statistically stored basal <
a>
dislocations may turn into geometrically necessary basal <
a>
edge dislocations during the initial stage of low-angle kink boundary formation. When a kink boundary is considered as a disclination, IGMA analysis capable of determining the lattice rotation axis and the angle is effective in evaluating the Frank vector of the kink boundary. -
C40/C11b超高温耐熱複相シリサイド合金における特異な「cross-lamellar microstructure」の発達 Invited
萩原幸司, 池西貴昭, 中野貴由
日本金属学会誌まてりあ 57 204 2018.05
Language：Japanese Publishing type：Research paper (scientific journal)
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金属積層造形法における形状・組織制御による異方性付与 Invited
萩原幸司, 石本卓也, 中野貴由
日本金属学会誌まてりあ 57 145 - 149 2018.04
Language：Japanese Publishing type：Research paper (scientific journal)
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チタン単結晶の塑性変形機構 Invited Reviewed
萩原幸司
軽金属 68 172 - 180 2018.04
Language：Japanese Publishing type：Research paper (scientific journal)
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Strain-rate dependence of deformation behavior of LPSO-phases Reviewed
Koji Hagihara, Zixuan Li, Michiaki Yamasaki, Yoshihito Kawamura, Takayoshi Nakano
Materials Letters 214 119 - 122 2018.03
Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier B.V.
This is the first report clarifying the influence of the strain rate on the deformation behavior of Mg-based long-period stacking ordered (LPSO) phases with 14H, 18R, and 10H structures. The flow stress by basal slip showed a weakly positive or negligible strain-rate dependence, while the flow stress accompanied by the formation of deformation kink bands showed a unique negative strain-rate dependence. These results give the first experimental evidence on the recent proposal that Zn and Y atoms segregate at the kink band boundaries and hinder their migration, from the viewpoint of the mechanical properties.
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Phonon excitations in a single crystal Mg<inf>85</inf>Zn<inf>6</inf>Y<inf>9</inf> with a synchronized long-period stacking ordered phase Reviewed
Shinya Hosokawa, Koji Kimura, Jens Rüdiger Stellhorn, Koji Yoshida, Koji Hagihara, Hitoshi Izuno, Michiaki Yamasaki, Yoshihito Kawamura, Yoji Mine, Kazuki Takashima, Hiroshi Uchiyama, Satoshi Tsutsui, Akihide Koura, Fuyuki Shimojo
Acta Materialia 146 273 - 279 2018.03
Language：English Publishing type：Research paper (scientific journal)
© 2018 Acta Materialia Inc. Inelastic X-ray scattering (IXS) experiments were carried out at room temperature at BL35XU of the SPring-8 on a single crystal Mg85Zn6Y9 alloy with a synchronized long-period stacking ordered (LPSO) phase of purely 18R type. The IXS measurements were carried out in both the longitudinal and transverse directions along the Γ-K and Γ-M (momentum vector q⊥ lattice axis c), and Γ-A (q∥c) directions for the energy transfers ω below 40 meV. Peaks arising from longitudinal and transverse acoustic (LA and TA) modes were clearly observed in the IXS spectra. The dispersion relations of the LA and TA modes in the Mg85Zn6Y9 LPSO alloy are mostly similar to those of previous INS data on single crystal pure Mg. New impurity-derived dispersion-less excitation modes are observed along all of the crystal directions at about 5, 10, and 17 meV. Partial vibrational density of states (vDOS) was obtained using an ab initio molecular dynamics simulation, and it was found that the ∼10 meV peak mainly originates from the phonon excitations inside the L12-type Zn6Y8 clusters and the ∼17 meV peak from those between the cluster and the host Mg atoms, and a small shoulder at 5 meV consists of motions of all the elements. These findings clarify that the dispersion-less modes mainly correspond to localized stretching and twisting modes around the impurity clusters in the LPSO alloys.
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Effect of scanning strategy on texture formation in Ni-25 at.%Mo alloys fabricated by selective laser melting Reviewed
Shi-Hai Sun, Koji Hagihara, Takayoshi Nakano
Materials and Design 140 307 - 316 2018.02
Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Ltd
Variations in the crystallographic texture in Ni-25 at.%Mo alloys fabricated by selective laser melting with different scanning strategies were designed for the first time. Single-crystalline-like texture with a short-range order of Mo atoms can be produced via bidirectional scanning along one axis (X-scan) and bidirectional scanning with a 90° rotation in each layer (XY-scan), while only fiber texture was formed in bidirectional scanning with a 67° rotation (Rot-scan). The aligned crystal orientation along the build direction can be varied by the scanning strategy
〈001〉 is preferred in the XY- and Rot-scan samples, while 〈101〉 is preferred in the X-scan sample. The controlling mechanisms of the texture, focusing on the preferential growth directions of the columnar cells and the following epitaxial growth, are discussed.
