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Zhang, Y.-J.*; Umeda, Takemasa*; Morooka, Satoshi; Harjo, S.; Miyamoto, Goro*; Furuhara, Tadashi*
Metallurgical and Materials Transactions A, 55(10), p.3921 - 3936, 2024/10
Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)Zhou, L.*; Zhang, H.*; Qin, T. Y.*; Hu, F. F.*; Xu, P. G.; Ao, N.*; Su, Y. H.; He, L. H.*; Li, X. H.*; Zhang, J. R.*; et al.
Metallurgical and Materials Transactions A, 55(7), p.2175 - 2185, 2024/07
Times Cited Count:3 Percentile:81.14(Materials Science, Multidisciplinary)Tsuru, Tomohito; Nishimura, Katsuhiko*; Matsuda, Kenji*; Nunomura, Norio*; Namiki, Takahiro*; Lee, S.*; Higemoto, Wataru; Matsuzaki, Teiichiro*; Yamaguchi, Masatake; Ebihara, Kenichi; et al.
Metallurgical and Materials Transactions A, 54(6), p.2374 - 2383, 2023/06
Times Cited Count:2 Percentile:33.88(Materials Science, Multidisciplinary)Although hydrogen embrittlement susceptibility of high-strength Al alloys is recognized as a critical issue in the practical use of Al alloys, identifying the hydrogen trapping or distribution has been challenging. In the present study, an effective approach based on experiment and simulation is proposed to explore the potential trap sites in Al alloys. Zero-field muon spin relaxation experiments were carried out for Al-0.5%Mg, Al-0.2%Cu, Al-0.15%Ti, Al-0.011%Ti, Al-0.28%V, and Al-0.015%V (at.%) in the temperature range from 5 to 300 K. The temperature variations of the dipole field widths have revealed three peaks for Al-0.5%Mg, four peaks for Al-0.2%Cu, three peaks for Al-0.011%Ti and Al-0.015%V. Atomic configurations of the muon trapping sites corresponding to the observed peaks are well assigned using the first-principles calculations for the trap energies of hydrogen around a solute and solute-vacancy pair. The extracted linear relationship between the muon
peak temperature and the trap energy enables us to explore the potential alloying elements and their complex that have strong binding energies with hydrogen in Al alloys.
Koga, Norimitsu*; Umezawa, Osamu*; Yamamoto, Masayuki*; Yamamoto, Takashi*; Yamashita, Takayuki; Morooka, Satoshi; Kawasaki, Takuro; Harjo, S.
Metallurgical and Materials Transactions A, 52(3), p.897 - 901, 2021/03
Times Cited Count:3 Percentile:18.44(Materials Science, Multidisciplinary)Ebihara, Kenichi; Sugiyama, Yuri*; Matsumoto, Ryosuke*; Takai, Kenichi*; Suzudo, Tomoaki
Metallurgical and Materials Transactions A, 52(1), p.257 - 269, 2021/01
Times Cited Count:9 Percentile:43.14(Materials Science, Multidisciplinary)We simulated the thermal desorption spectra of a small-size iron specimen to which was applied during charging with hydrogen atoms using a model incorporating the behavior of vacancies and vacancy clusters. The model considered up to vacancy clusters , which is composed of nine vacancies and employed the parameters based on atomistic calculations, including the H trapping energy of vacancies and vacancy clusters that we estimated using the molecular static calculation. As a result, we revealed that the model could, on the whole, reproduced the experimental spectra except two characteristic differences, and also the dependence of the spectra on the aging temperature. By examining the cause of the differences, the possibilities that the diffusion of clusters of
and
is slower than the model and that vacancy clusters are generated by applying strain and H charging concurrently were indicated.
Lam, T.-N.*; Tsai, C.-W.*; Chen, B.-K.*; Lai, B.-H.*; Liu, H.-C*; Kawasaki, Takuro; Harjo, S.; Lin, B.-H.*; Huang, E.-W.*
Metallurgical and Materials Transactions A, 51(10), p.5023 - 5028, 2020/10
Times Cited Count:14 Percentile:59.82(Materials Science, Multidisciplinary)Saito, Kei*; Hirade, Tetsuya; Takai, Kenichi*
Metallurgical and Materials Transactions A, 50(11), p.5091 - 5102, 2019/11
Times Cited Count:34 Percentile:84.37(Materials Science, Multidisciplinary)An attempt was made to separate and identify hydrogen peaks desorbed from lattice defects formed by plastic-strain in the presence of hydrogen in tempered martensitic steel showing quasi-cleavage fracture using thermal desorption spectroscopy from a low temperature (L-TDS) and positron annihilation spectroscopy (PAS). The L-TDS results made it possible to separate two peaks, namely, that of the original desorption and also that of new desorption. The PAS results revealed that the new desorption obtained by L-TDS corresponded to vacancy-type defects. Hydrogen enhanced vacancy-type defect concentration, approximately 10 order in terms of atomic ratio, formed within 1.5 mm from the fracture surface, These results indicate that the accumulation of excess vacancy-type defects enhanced by hydrogen in the local region can lead to nanovoid nucleation and coalescence in plastic deformation, resulting in quasi-cleavage fracture of tempered martensitic steel.
Harjo, S.; Kawasaki, Takuro; Tomota, Yo*; Gong, W.*; Aizawa, Kazuya; Tichy, G.*; Shi, Z.*; Ungr, T.*
Metallurgical and Materials Transactions A, 48(9), p.4080 - 4092, 2017/09
Times Cited Count:60 Percentile:91.92(Materials Science, Multidisciplinary)Ungr, T.*; Harjo, S.; Kawasaki, Takuro; Tomota, Yo*; Rib
rik, G.*; Shi, Z.*
Metallurgical and Materials Transactions A, 48(1), p.159 - 167, 2017/01
Times Cited Count:54 Percentile:90.71(Materials Science, Multidisciplinary)Sato, Yutaka*; Kokawa, Hiroyuki*; Fujii, Hiromichi*; Yano, Yasuhide; Sekio, Yoshihiro
Metallurgical and Materials Transactions A, 46(12), p.5789 - 5800, 2015/12
Times Cited Count:18 Percentile:59.68(Materials Science, Multidisciplinary)Dissimilar friction stir welding (FSW) of an 11% Cr ferritic/martensitic stee (PNC-FMS) to 316-grade austenitic stainless steel was attempted with a view to its potential application to the wrapper tubes of next-generation fast reactors. The mechanical properties and microstructure of the resulting welds were systematically examined, which revealed that FSW produces a defect-free stir zone in which material intermixing is notably absent. That is, both steels are separately distributed along a zigzagging interface in the stir zone when PNC-FMS is placed on the retreating side, with the tool plunging at the butt line. This interface did not act as a fracture site during small-sized tensile testing of the stir zone. Furthermore, the microstructure of the stir zone was refined in both the PNC-FMS and 316 stainless steel sides, resulting in improved mechanical properties over the respective base material regions.
Yamaguchi, Masatake
Metallurgical and Materials Transactions A, 42(2), p.319 - 329, 2011/02
Times Cited Count:143 Percentile:98.07(Materials Science, Multidisciplinary)Yamaguchi, Masatake; Ebihara, Kenichi; Itakura, Mitsuhiro; Kadoyoshi, Tomoko*; Suzudo, Tomoaki; Kaburaki, Hideo
Metallurgical and Materials Transactions A, 42(2), p.330 - 339, 2011/02
Times Cited Count:129 Percentile:97.61(Materials Science, Multidisciplinary)Nishiyama, Yutaka; Liu, X.*; Kameda, Jun*
Metallurgical and Materials Transactions A, 39(5), p.1118 - 1131, 2008/05
Times Cited Count:2 Percentile:20.16(Materials Science, Multidisciplinary)