Enhanced work hardening in ferrite and austenite of duplex stainless steel at 200 K; neutron diffraction study

Yamashita, Takayuki*; Koga, Norimitsu*; Mao, W.*; Gong, W.; Kawasaki, Takuro; Harjo, S.; Fujii, Hidetoshi*; Umezawa, Osamu*

Materials Science and Engineering A, 941, p.148602_1 - 148602_11, 2025/09

https://doi.org/10.1016/j.msea.2025.148602

Grain refinement of dual phase steel maximizes deformation ability of martensite, leading to simultaneous enhancement of strength and ductility

Park, M.-H.*; Shibata, Akinobu*; Harjo, S.; Tsuji, Nobuhiro*

Acta Materialia, 292, p.121061_1 - 121061_13, 2025/06

https://doi.org/10.1016/j.actamat.2025.121061

Experimental investigation of phase transformations in steel using X-ray and neutron diffraction

Tomota, Yo*; Harjo, S.; Xu, P. G.; Morooka, Satoshi; Gong, W.; Wang, Y.*

Metals, 15(6), p.610_1 - 610_19, 2025/05

https://doi.org/10.3390/met15060610

Density of a molten stainless steel-BC alloy measured in the electrostatic levitation furnace onboard the international space station

Ishikawa, Takehiko*; Oda, Hirohisa*; Koyama, Chihiro*; Shimonishi, Rina*; Ikeuchi, Rumiko*; Paradis, P.-F.*; Okada, Jumpei*; Fukuyama, Hiroyuki*; Yamano, Hidemasa

International Journal of Microgravity Science and Application, 42(2), p.420202_1 - 420202_10, 2025/04

https://doi.org/10.15011/jasma.42.420202

Elemental composition analysis of main structural materials of JMTR

Nagata, Hiroshi; Kochiyama, Mami; Chinone, Marina; Sugaya, Naoto; Nishimura, Arashi; Ishikawa, Joji; Sakai, Akihiro; Ide, Hiroshi

JAEA-Data/Code 2024-016, 44 Pages, 2025/03

JAEA-Data-Code-2024-016.pdf:3.54MB

The elemental composition of the structural materials of nuclear reactor facilities is used as one of the important parameters in activation calculations that are evaluated when formulating decommissioning plans. Regarding the elemental composition of aluminum alloys and other materials used as structural materials for test and research reactors, sufficient data is not available regarding elements other than the major elements. For this reason, samples were collected from aluminum alloy, beryllium, hafnium, and other materials that have been used as the main structural materials of JMTR (Japan Materials Testing Reactor), and their elemental compositions were analyzed. This report summarizes the elemental composition data of 78 elements obtained in FY2023.

Effect of grain refinement on transgranular stress corrosion cracking in SUS304L under boiling water reactor conditions

Hirota, Noriaki; Nakano, Hiroko; Takeda, Ryoma; Ide, Hiroshi; Tsuchiya, Kunihiko; Kobayashi, Yoshinao*

Zairyo No Kagaku To Kogaku, 61(6), p.248 - 252, 2024/12

A comparative analysis of the 0.2 % yield stress in SUS304L stainless steel revealed that lower strain rates and higher temperatures significantly reduce yield stress. Grain refinement from 68.6 m to 0.59 m minimally impacted the rate of yield stress reduction at slower strain rates. However, finer grains showed a decrease in yield stress at reactor operating temperature compared to room temperature. In slow strain rate tests under conditions promoting intragranular stress corrosion cracking (SCC), SUS304L with grain sizes of 28.4 m or smaller exhibited similar fracture strains comparable to those at reactor operating temperatures, whereas coarse-grained SUS304L showed reduced fracture strain. Microstructural analysis showed that in smaller grains, over 87 % of the fracture surface was ductile. In particular, SUS304L with 0.59 m grains exhibited a higher presence of {111} / 3 boundaries, which decreased with grain growth. These results indicate that grain refinement will suppress intragranular SCC by slowing corrosion progression through increased {111} / 3 boundaries.

Deformation behavior of ultrafine-grained TRIP steel observed by neutron diffraction

Harjo, S.; Mao, W.*; Gong, W.; Kawasaki, Takuro

Proceedings of the 7th International Symposium on Steel Science (ISSS 2024), p.205 - 208, 2024/11

https://doi.org/10.2355/isijisss.2024.0_205

Martensitic transformation-governed Luders deformation enables large ductility and late-stage strain hardening in ultrafine-grained austenitic stainless steel at low temperatures

Mao, W.*; Gao, S.*; Gong, W.; Kawasaki, Takuro; Ito, Tatsuya; Harjo, S.; Tsuji, Nobuhiro*

Acta Materialia, 278, p.120233_1 - 120233_13, 2024/10

https://doi.org/10.1016/j.actamat.2024.120233

Anisotropic creep property related to non-spherical shape of mechanically alloyed powder of oxide dispersion strengthened F82H

Sakasegawa, Hideo; Nakajima, Motoki*; Kato, Taichiro*; Nozawa, Takashi*; Ando, Masami*

Materials Today Communications (Internet), 40, p.109659_1 - 109659_8, 2024/08

https://doi.org/10.1016/j.mtcomm.2024.109659

Nanometric oxide particles play an important role in improving the creep property of Oxide Dispersion Strengthened (ODS) steels. In our previous research, we examined a microstructural feature known as prior particle boundary (PPB). PPB refers to the surface of mechanically alloyed (MA) powders before consolidation. We revealed that the ODS steel with fine PPBs produced from smaller MA powders, exhibited shorter creep rupture times, compared to that with coarse PPBs produced from larger MA powders. The size of MA powders had an impact on the creep property. In this study, we examined the shape of MA powders, which were non-spherical shapes. Such shapes have the potential to induce anisotropic creep behavior. We conducted small punch creep tests on specimens with two different orientations to study the possible anisotropy. The results revealed that the creep rupture times varied depending on the orientation of specimen, thus indicating anisotropic creep property.

Effects of loading direction on the anisotropic tensile properties of duplex stainless steels based on phase strains obtained by in situ neutron diffraction experiments

Matsushita, Akira*; Tsuchida, Noriyuki*; Ishimaru, Eiichiro*; Hirakawa, Naoki*; Gong, W.; Harjo, S.

Journal of Materials Engineering and Performance, 33(13), p.6352 - 6361, 2024/07

https://doi.org/10.1007/s11665-023-08424-0