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Harjo, S.; Gong, W.; Kawasaki, Takuro; Morooka, Satoshi; Yamashita, Takayuki*
ISIJ International, 62(10), p.1990 - 1999, 2022/10
Times Cited Count：1 Percentile：0(Metallurgy & Metallurgical Engineering)Yoshida, Masayuki*; Nishihata, Itsuki*; Matsuda, Tomoki*; Ito, Yusuke*; Sugita, Naohiko*; Shiro, Ayumi*; Shobu, Takahisa; Arakawa, Kazuto*; Hirose, Akio*; Sano, Tomokazu*
Journal of Applied Physics, 132(7), p.075101_1 - 075101_9, 2022/08
Times Cited Count：5 Percentile：64.66(Physics, Applied)Komatsu, Yuya*; Shimizu, Ryota*; Sato, Ryuhei*; Wilde, M.*; Nishio, Kazunori*; Katase, Takayoshi*; Matsumura, Daiju; Saito, Hiroyuki*; Miyauchi, Masahiro*; Adelman, J. R.*; et al.
Chemistry of Materials, 34(8), p.3616 - 3623, 2022/04
Times Cited Count：9 Percentile：76.65(Chemistry, Physical)Zhang, X. X.*; Knoop, D.*; Andr
, H.*; Harjo, S.; Kawasaki, Takuro; Lutz, A.*; Lahres, M.*
International Journal of Plasticity, 140, p.102972_1 - 102972_20, 2021/05
Times Cited Count：28 Percentile：94.42(Engineering, Mechanical)
WB-STEM observation of dislocation loop behavior in reactor pressure vessel steel during post-irradiation annealingDu, Y.*; Yoshida, Kenta*; Shimada, Yusuke*; Toyama, Takeshi*; Inoue, Koji*; Arakawa, Kazuto*; Suzudo, Tomoaki; Milan, K. J.*; Gerard, R.*; Onuki, Somei*; et al.
Materialia, 12, p.100778_1 - 100778_10, 2020/08
In order to ensure the integrity of the reactor pressure vessel in the long term, it is necessary to understand the effects of irradiation on the materials. In this study, irradiation-induced dislocation loops were observed in neutron-irradiated reactor pressure vessel specimens during annealing using our newly developed WB-STEM. It was confirmed that the proportion of 
loops increased with increasing annealing temperature. We also succeeded in observing the phenomenon that two 
loops collide into a loop. Moreover, a phenomenon in which dislocation loops decorate dislocations was also observed, and the mechanism was successfully explained by molecular dynamics simulation.
Woo, W.*; Naeem, M.*; Jeong, J.-S.*; Lee, C.-M.*; Harjo, S.; Kawasaki, Takuro; He, H.*; Wang, X.-L.*
Materials Science & Engineering A, 781, p.139224_1 - 139224_7, 2020/04
Times Cited Count：39 Percentile：93.25(Nanoscience & Nanotechnology)Shobu, Takahisa; Shiro, Ayumi*; Yoshida, Yutaka*
Zairyo, 69(4), p.343 - 347, 2020/04
Dislocation density is a very important physical quantity in the evaluation of fatigue of metallic materials. Generally, the dislocation density is evaluated by a scanning electron microscope. Recently, a method generated the dislocation density from the width of the X-ray diffraction profile has been proposed. In this study, we report the application of this technology to synchrotron radiation. Five diffraction profiles were obtained with a two-dimensional detector during tensile loading of the austenitic stainless steel SUS316L, and the dislocation density was calculated from the line profile analysis. As a result, the dislocation density increased sharply after plastic deformation, and the value was in good agreement with the result separately measured with a scanning electron microscope. In the future, it is expected that the line profile analysis will contribute to the elucidation of the mechanism of fatigue fracture by measuring the dislocation density from the local area in materials.
Kasahara, Shigeki; Chimi, Yasuhiro; Hata, Kuniki; Hanawa, Satoshi
Zairyo To Kankyo, 68(9), p.240 - 247, 2019/09
In order to study environment assisted cracking mechanism of stainless steel under BWR primary coolant condition, effects of applied load on oxidation in the vicinity of crack tips of CT specimens were evaluated. Loaded CT specimens were immersed in an aqueous condition at 290
C as a simulated BWR coolant condition, and microstructural observation on oxide near the tips of pre-cracks was carried out. Oxide inner layers, which consisted of fine grain magnetite containing Fe and Cr were formed, and oxide outer layers consisting of large grains of Fe
O
were observed to cover the inner layers. FEM analysis of stress and strain in the loaded CT specimen suggests that both of dislocations due to localized plastic deformation and elastic strain could play important roles to accelerate inner oxide formation in the vicinity of the crack tip of the specimens.
Suzudo, Tomoaki; Onitsuka, Takashi*; Fukumoto, Kenichi*
Modelling and Simulation in Materials Science and Engineering, 27(6), p.064001_1 - 064001_15, 2019/08
Times Cited Count：16 Percentile：65.43(Materials Science, Multidisciplinary)Plasticity of body-centered-cubic (BCC) metals at low temperatures is determined by screw dislocation kinetics. Because the core of screw dislocation in these metals has non-planar structure, its motion is complex and unpredictable. For example, although density functional theory (DFT) predicts slip on a { 110 } plane, the actual slip plane at elevated temperatures departs from the prediction, its mechanism having been a mystery for decades. Here we conduct a series of molecular dynamics simulations to track the screw dislocation motion and successfully reproduced the transition of the slip plane. We then devised an algorithm to scrutinize the activation of dislocation jump over the Peierls barrier and discovered the possible origin of this unexpected phenomenon, i.e., a large fluctuation leads to the kink-pair nucleation for the cross-slip jump without transition of dislocation core structure.
Tomota, Yo*; Ojima, Mayumi*; Harjo, S.; Gong, W.*; Sato, Shigeo*; Ung
r, T.*
Materials Science & Engineering A, 743, p.32 - 39, 2019/01
Times Cited Count：25 Percentile：81.14(Nanoscience & Nanotechnology)Harjo, S.; Kawasaki, Takuro; Tomota, Yo*; Gong, W.
Materials Science Forum, 905, p.46 - 51, 2017/08
Tomota, Yo*; Sato, Shigeo*; Harjo, S.
Tetsu To Hagane, 103(2), p.73 - 85, 2017/01
Times Cited Count：18 Percentile：62.47(Metallurgy & Metallurgical Engineering)Harjo, S.; Kawasaki, Takuro; Gong, W.; Aizawa, Kazuya
Journal of Physics; Conference Series, 746(1), p.012046_1 - 012046_7, 2016/10
Times Cited Count：5 Percentile：88.68(Physics, Nuclear)Xiong, Z.; Naoe, Takashi; Wan, T.; Futakawa, Masatoshi; Maekawa, Katsuhiro*
Procedia Engineering, 101, p.552 - 560, 2015/03
Times Cited Count：2 Percentile：62.07(Engineering, Multidisciplinary)Very high-cycle fatigue behaviour of SUS316L, which is used as the structural material of the spallation neutron sources, was investigated through the ultrasonic fatigue test with the strain rate of 10
s
. Cross-sectional hardness distributions of the fatigue-failed specimens for solution annealed (SA) and cold worked (CW) 316L were measured to understand the cyclic hardening or softening. In addition, the tensile tests of the fatigue-failed specimens were performed at room temperature. Furthermore, the nonlinear ultrasonic system was used for evaluating the dislocation density variation. The results showed the cyclic hardening in the region of very high-cycle fatigue in the case of SA. In contrast, in the case of 10%CW, cyclic softening occurred when the number of cycles below 10
and followed by cyclic hardening. In the case of 20%CW, cyclic softening was observed when the number of cycles below 10
, while cyclic hardening occurred subsequently.
Kumagai, Masayoshi*; Akita, Koichi; Imafuku, Muneyuki*; Oya, Shinichi*
Advanced Materials Research, 996, p.39 - 44, 2014/08
Times Cited Count：6 Percentile：93.33(Engineering, Mechanical)The microstructural features of shot and laser peened austenitic stainless steels were studied using line profile analysis with X-rays. Although both specimens had similar residual stress profiles toward the depth direction, the microstructural features were different not only on the original surfaces of the specimens but also to several micrometers in depth. The dislocation densities of the SP specimen were greater than that of the LP specimen. And the crystallite sizes of the SP specimen were smaller than that of the LP specimen.
Wakai, Eiichi; Hashimoto, Naoyuki*; Robertson, J. P.*; Sawai, Tomotsugu; Hishinuma, Akimichi
Journal of Nuclear Materials, 307-311(Part.1), p.352 - 356, 2002/12
Times Cited Count：11 Percentile：58.04(Materials Science, Multidisciplinary)no abstracts in English
ion irradiationWakai, Eiichi; Ezawa, Tadashi*; Imamura, Junko*; Takenaka, Tsuyoshi*; Tanabe, Tetsuo*; Oshima, Ryuichiro*
Journal of Nuclear Materials, 307-311(Part.1), p.367 - 373, 2002/12
Times Cited Count：29 Percentile：84.85(Materials Science, Multidisciplinary)no abstracts in English
Tokiwa, Yoshifumi; Ikeda, Shugo*; Haga, Yoshinori; Okubo, Tomoyuki*; Iizuka, Tomoya*; Sugiyama, Kiyohiro*; Nakamura, Akio; Onuki, Yoshichika
Journal of the Physical Society of Japan, 71(3), p.845 - 851, 2002/03
Times Cited Count：40 Percentile：81.12(Physics, Multidisciplinary)We succeeded in growing a high-quality single crystal of an antiferromagnet UPtGa by the self-flux method, and measured the magnetic susceptibility, electrical resistivity, specific heat and de Haas-van Alphen (dHvA) oscillation. We found an antiferromagnetic transition at 26K from the magnetic susceptibility and electrical resistivity measurements. Six dHvA branches were observed, ranging from 1.14
10 to 1.1310
Oe. Fermi surfaces consist of two nearly cylindrical and two spherical Fermi surfaces. The cyclotron mass is large, ranging from 10 to 24 
, which is consistent with the electronic specific heat coefficient 
= 57 mJ/K
mol.
ion irradiationWakai, Eiichi; Hishinuma, Akimichi; Abe, Hiroaki; Takaki, Seiichi*; Abiko, Kenji*
Materials Transactions, JIM, 41(9), p.1176 - 1179, 2000/09
no abstracts in English
*; *; *; *; Hasegawa, Makoto; Hirano, Koichiro
JNC TY9400 2000-007, 50 Pages, 2000/03
JNC-TY9400-2000-007.pdf:1.29MB
no abstracts in English
