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相馬 康孝; 小松 篤史; 五十嵐 誉廣
Corrosion Science, 265, p.113182_1 - 113182_13, 2026/06
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)This study investigates the ion enrichment behavior inside stainless steel crevices in a very dilute solution (water containing 10~ppb Cl
), under conditions where no localized corrosion occurred. In~situ measurements of the crevice potential (
) and solution conductivity (
) were performed and analyzed using a finite element model. In crevices with sufficiently large depth-to-gap ratios (
), an initial decrease in increased the potential difference between the crevice interior and the external surface (
), thereby promoting an increase in due to chloride accumulation. At later stages, increased owing to a decrease in pH and a reduction in the IR drop, causing to peak and subsequently decrease. Larger ratios resulted in lower and higher . For the largest condition investigated (
~mm, 
m), and reached 0.218~V and 195.3~
S
cm
, respectively, after 
~s, corresponding to an estimated chloride enrichment factor exceeding 
. These results indicate that a driving force for chloride enrichment can be sustained for long durations even in passive crevices.
neutron diffraction experiments土田 紀之*; 藤田 晃徳*; 平川 直樹*; 濱田 純一*; 石丸 栄一郎*; Gong, W.; 川崎 卓郎; Harjo, S.
Materials Characterization, 236, p.116436_1 - 116436_13, 2026/06
被引用回数：1 パーセンタイル：0.00(Materials Science, Multidisciplinary)This study investigated the transformation-induced plasticity (TRIP) effect in duplex stainless steel (DSS), focusing on the influence of deformation temperature on the mechanical properties of 24Cr-5Ni-0.18N DSS. The steel showed an excellent balance of tensile strength and uniform elongation below 183 K due to deformation-induced martensitic transformation (DIMT) of the austenite (
) phase. The superior TRIP effect was attributed not only to DIMT and enhanced stress and work hardening at lower temperatures, but also to changes in phase interactions and texture evolution. DIMT suppressed crystal rotation, altered stress partitioning among constituent phases, and weakened the texture of the 
and ' phases. In JIS-SUS329J4L, phase stress, work hardening, and KAM values increased with decreasing temperature, while the texture weakened.
neutron diffraction study山下 享介*; 小山 元道*; Gong, W.; 川崎 卓郎; Harjo, S.; 潮田 浩作*; 藤井 英俊*
ISIJ International, 66(4), p.477 - 488, 2026/03
被引用回数：0 パーセンタイル：0.00(Metallurgy & Metallurgical Engineering)This study investigated strengthening mechanisms in friction stir welded (FSW) duplex stainless steel (DSS) using in situ neutron diffraction during tensile testing. Two welding conditions, FSW300 and FSW600, produced significant grain refinement, with grains below 1 m in FSW300. Both conditions increased yield and tensile strength but reduced elongation compared with the base metal (BM), while FSW300 retained higher total elongation than FSW600. Neutron diffraction revealed that was the harder phase in the BM, whereas became the harder phase after FSW. Phase stress analysis showed that was more sensitive to grain refinement strengthening, shifting the dominant strengthening contribution from to . Although stacking faults in increased after FSW, work hardening of decreased, while showed enhanced texture development and dislocation accumulation.
山下 勇人; 豊田 晃大; 鬼澤 高志; 山本 賢二*; 久保 幸士*
日本機械学会論文集(インターネット), 92(955), p.25-00176_1 - 25-00176_13, 2026/03
本研究では改良9Cr-1Mo鋼の溶接継手及び補修位置と補修回数を変えた補修溶接継手を製作し、それらのクリープ強度を調査した。そして、補修溶接継手がクリープ強度に及ぼす影響を金属組織観察等により考察し、補修溶接法を開発した。
伊東 達矢; 小川 祐平*; Gong, W.; 川崎 卓郎; 柴田 曉伸*; Harjo, S.
Scripta Materialia, 273, p.117084_1 - 117084_6, 2026/03
被引用回数：5 パーセンタイル：60.79(Nanoscience & Nanotechnology)The effect of solute hydrogen on stacking fault evolution in austenitic steels remains debated. In this study, the changes in stacking fault probability in the 
111
//loading direction grains family (
) of hydrogen-charged and non-charged Fe-24Cr-19Ni austenitic steels were evaluated using neutron diffraction during tensile deformation at 223 and 177 K. When values were plotted against macroscopic strain, hydrogen apparently enhanced stacking fault evolution. However, when identical data were translated into the form of versus stress, the superficial hydrogen-effect on notably disappeared. Rather, deformation temperature played more predominant role - lower temperature led to higher regardless of hydrogen-charging, reflecting the reduction of stacking fault energy with decreasing temperature. These findings demonstrate that hydrogen has a minor effect on stacking fault evolution compared with temperature and applied stress.
入澤 恵理子; 加藤 千明
Corrosion Science, 256, p.113173_1 - 113173_16, 2025/11
被引用回数：6 パーセンタイル：77.29(Materials Science, Multidisciplinary)This study investigates the corrosion behavior of extra-high-purity Type 316 austenitic (316EHP) stainless steel with reduced impurity segregation at the grain boundaries in a liquid lead-bismuth eutectic (LBE) at 530
C to evaluate (1) the resistance of the steel to intergranular oxidation in the LBE with oxygen saturation and (2) its dissolution corrosion resistance at lower oxygen concentrations than the equilibrium oxygen potential of magnetite. Under oxygen saturation conditions in the LBE, 316EHP generated protective uniform oxide layers without severe intragranular oxidation. Compared with the case of the conventional 316L stainless steel, enhanced Cr diffusion along the grain boundaries in 316EHP considerably improved the intergranular-oxidation resistance of the steel. However, in the LBE with a low oxygen concentration, 316EHP exhibited high susceptibility to dissolution corrosion, thus undergoing a rapid intergranular attack particularly for short exposure durations, and island-like ferritic particles were formed for long exposure durations. Future studies should explore the optimal oxygen concentrations for oxide scale formation and the long-term corrosion behavior of the steel in dynamic LBE systems.
大谷 恭平; 五十嵐 誉廣
Journal of the Electrochemical Society, 172(9), p.091503_1 - 091503_8, 2025/09
被引用回数：0 パーセンタイル：0.00(Electrochemistry)This study investigates how liquid film thickness and flow velocity influence the cathodic reaction rate of carbon steel under flowing liquid film conditions, with relevance to the Fukushima Daiichi Nuclear Power Station. A custom-built flow system was developed to independently control both film thickness and velocity. Electrochemical tests were conducted using carbon steel and pure silver electrodes to assess the impact of oxygen transport. Results showed that the cathodic limiting current density increased as flow velocity increased and film thickness decreased. However, for carbon steel, the experimental values deviated from theoretical predictions due to the formation of corrosion products on the electrode surface, which hinder oxygen transport. This suppressed the expected increase in current density at higher flow velocities. In contrast, pure silver, which does not form corrosion products, showed experimental values in good agreement with theory.
neutron diffraction study山下 享介*; 古賀 紀光*; Mao, W.*; Gong, W.; 川崎 卓郎; Harjo, S.; 藤井 英俊*; 梅澤 修*
Materials Science & Engineering A, 941, p.148602_1 - 148602_11, 2025/09
被引用回数：4 パーセンタイル：70.22(Nanoscience & Nanotechnology)Ferrite-austenite duplex stainless steels offer excellent strength and ductility, making them suitable for extreme environments. In this study, neutron diffraction during tensile testing at 293 K and 200 K was used to investigate stress partitioning and phase-specific deformation. Phase stress was calculated using a texture-compensated method. At both temperatures, ferrite showed higher phase stress than austenite, acting as the harder phase. At 200 K, both phases exhibited increased strength and work hardening. Austenite showed significant stacking fault formation alongside dislocation migration, while ferrite retained its dislocation-based deformation mode, becoming more effective. Stress contributions from both phases were comparable. No martensitic transformation occurred. Strengthening and enhanced work hardening in both phases led to high strength at 200 K, with ductility similar to that at 293 K.
伊東 達矢; 小川 祐平*; Gong, W.; Mao, W.*; 川崎 卓郎; 岡田 和歩*; 柴田 曉伸*; Harjo, S.
波紋, 35(3), p.129 - 133, 2025/08
Recent studies have shown that the addition of hydrogen to SUS310S stainless steel (Fe-24Cr-19Ni, mass%) simultaneously enhances both strength and ductility, indicating a phenomenon contrary to the conventional understanding of hydrogen embrittlement. In this study, we investigated the underlying mechanism through neutron diffraction experiments during tensile deformation using TAKUMI at the MLF of J-PARC. The results revealed that solid-solution strengthening by hydrogen plays the most significant role in improving the mechanical properties. Solute hydrogen atoms distort the lattice to suppress dislocation motion, thereby increasing the strength. The raised stress in the hydrogen charged sample enables the onset of deformation twinning at a smaller strain compared to the non-hydrogen charged sample. Consequently, the twinning-induced plasticity effect contributes more significantly to work hardening and the improvement of uniform elongation due to the solid-solution strengthening by hydrogen. These findings suggest a new pathway for the effective utilization of hydrogen in austenitic steels.
豊田 晃大; 今川 裕也; 鬼澤 高志; 鈴木 章裕*
Proceedings of the ASME 2025 Pressure Vessels & Piping Conference (PVP2025) (Internet), 8 Pages, 2025/07
Sodium-cooled fast reactors (SFRs) have been focused on to realize a decarbonized society and are being developed in Japan. Since there is concern that Mod.9Cr-1Mo steel, a candidate material for SFR steam generators, will be affected by thermal aging and lose strength when used at high temperatures for long periods of time, it is important to evaluate the effect of thermal aging over long periods of time. Mod.9Cr-1Mo steel requires post weld heat treatment (PWHT) after welding. In the Japan Society of Mechanical Engineers (JSME)code, Rules on the Design and Construction of Nuclear Power Plants, the allowable values for base metal are set using materials that have undergone stress relief heat treatment (SR) after normalizing and tempering (NT) to simulate the thermal history of the PWHT. This paper describes the post aging tensile strength of materials subjected to prolonged thermal aging in order to provide a more detailed evaluation of the effects of thermal aging on Mod. 9Cr-1Mo steels subjected to NT+SR than has been done in the past. The evaluation in this paper used tensile test results of material that had been actually thermal aged at 550C for approximately 200,000 hours. The results of post aging tensile tests showed that there was a difference in strength loss after aging between the NT materials and NT+SR materials. This paper discusses the differences between NT materials and NT+SR materials from the tensile test results obtained and identifies issues that need to be resolved for further analysis.
Mao, W.*; Gong, W.; 川崎 卓郎; Gao, S.*; 伊東 達矢; 山下 享介*; Harjo, S.; Zhao, L.*; Wang, Q.*
Scripta Materialia, 264, p.116726_1 - 116726_6, 2025/07
被引用回数：3 パーセンタイル：46.97(Nanoscience & Nanotechnology)An ultrafine-grained 304 austenitic stainless steel exhibited pronounced serrated Luders deformation at 20 K, with stress and temperature oscillations reaching 200 MPa and 20 K. 
neutron diffraction and digital image correlation revealed discontinuous Luders band propagation and burst martensite formation. During deformation, austenite phase stress remained lower than at upper yielding, indicating elastic behavior. Notably, martensite phase stress stayed lower than austenite until fracture, likely due to stress relaxation from burst martensitic transformation at 20 K. The low martensite stress delayed brittle fracture until austenite plastically yielded during uniform deformation.
Park, M.-H.*; 柴田 曉伸*; Harjo, S.; 辻 伸泰*
Acta Materialia, 292, p.121061_1 - 121061_13, 2025/06
被引用回数：52 パーセンタイル：99.57(Materials Science, Multidisciplinary)Dual-phase (DP) steel, composed of soft ferrite and hard martensite, offers excellent strength-ductility balance and low cost. This study found that refining the DP microstructure enhanced both yield strength and strain hardening, improving strength and ductility. Digital image correlation (DIC) revealed strain localization in ferrite, but refinement reduced strain differences between ferrite and martensite, suppressing crack initiation. More ferrite/martensite interfaces promoted plasticity in martensite via enhanced deformation constraint. neutron diffraction showed martensite bore higher phase stress, which increased with refinement. By combining -DIC and neutron data, individual stress-strain curves for ferrite and martensite were constructed for the first time, explaining the strength-ductility synergy through interphase constraint. These findings offer guidance for designing heterostructured materials to overcome the strength-ductility trade-off.
豊田 晃大; 鬼澤 高志; 若井 栄一*
Research & Development in Material Science (Internet), 21(5), p.2632 - 2637, 2025/06
316FR steel, a modification of 316 austenitic stainless steel, will be used as a structural material in the sodium cooled fast reactor (SFR), one of the initiatives being developed in Japan to achieve carbon neutrality in order to combat global warming. To withstand the high-temperature operating environment of the SFR, the alloy design of the 316FR steel has been optimized to have high creep strength for a long time with controlled precipitation by optimizing the alloy composition. In order to clarify that 316FR steel can maintain its properties under the high temperature (around 550C) irradiation environment of the SFR, the authors mainly conducted in-situ observations under electron beam irradiation at high temperatures to investigate in detail the irradiation effects on the precipitates (mainly carbides), which are characteristic of 316FR steel. As a result, it was found that the precipitates in 316FR steel are more stable than those in type 304 stainless steel under irradiation without coarsening at grain boundaries or within grains. The characteristics and attractiveness of 316FR steel, the results obtained, and the mechanism of creep behavior under irradiation are also explained.
青山 高士; 上野 文義; 佐藤 智徳; 加藤 千明; 佐野 成人; 山下 直輝; 大谷 恭平; 五十嵐 誉廣
Annals of Nuclear Energy, 214, p.111229_1 - 111229_6, 2025/05
被引用回数：0 パーセンタイル：0.00(Nuclear Science & Technology)To elucidate the effect of dissolved radionuclides on corrosion of carbon steels and on formation of corrosion products of carbon steel, corrosion tests and imaging plate analysis were conducted. Carbon steel samples immersed in 10 mM NaCl containing 
Sr and 
Cs were analyzed using an imaging plate. As a result, the distribution of Sr or Cs in the corrosion products formed on carbon steel was successfully visualized. Furthermore, the radioactivity of the corroded specimens was calculated from calibration curves prepared using a Sr standard.
友田 陽*; Harjo, S.; 徐 平光; 諸岡 聡; Gong, W.; Wang, Y.*
Metals, 15(6), p.610_1 - 610_19, 2025/05
被引用回数：4 パーセンタイル：35.62(Materials Science, Multidisciplinary)Lattice parameters of product and matrix phases in steels have been measured using in situ X-ray and neutron diffraction during forward and reverse transformations. These parameters are influenced by temperature, transformation-induced internal stresses, alloying element partitioning, crystal defects, and magnetic strains. Disentangling these contributions is essential for understanding lattice behavior. This review explores internal strain (stress) associated with ferrite, pearlite, bainite, martensite, and reverse austenite transformations, emphasizing the distinction between diffusional and displacive mechanisms. It also examines how plastic deformation of austenite affects subsequent bainite or martensite formation. The roles of dislocations and vacancies are identified as critical areas for further research.
neutron diffraction study伊東 達矢; 小川 祐平*; Gong, W.; Mao, W.*; 川崎 卓郎; 岡田 和歩*; 柴田 曉伸*; Harjo, S.
Acta Materialia, 287, p.120767_1 - 120767_16, 2025/04
被引用回数：24 パーセンタイル：98.39(Materials Science, Multidisciplinary)Incorporating solute hydrogen into Fe-Cr-Ni-based austenitic stainless steels enhances both strength and ductility, providing a promising solution to hydrogen embrittlement by causing solid-solution strengthening and assisting deformation twinning. However, its impacts on the relevant lattice defects evolution (
, dislocations, stacking faults, and twins) during deformation remains unclear. This study compared the tensile deformation behavior in an Fe-24Cr-19Ni (mass%) austenitic steel with 7600 atom ppm hydrogen-charged (H-charged) and without hydrogen-charged (non-charged) using neutron diffraction. Hydrogen effects on the lattice expansion, solid-solution strengthening, stacking fault probability, stacking fault energy, dislocation density, and strain/stress for twin evolution were quantitatively evaluated to link them with the macroscale mechanical properties. The H-charged sample showed improvements in yield stress, flow stress, and uniform elongation, consistent with earlier findings. However, solute hydrogen exhibited minimal influences on the evolution of dislocation and stacking fault. This fact contradicts the previous reports on hydrogen-enhanced dislocation and stacking fault evolutions, the latter of which can be responsible for the enhancement of twinning. The strain for twin evolution was smaller in the H-charged sample compared to the non-charged one. Nevertheless, when evaluated as the onset stress for twin evolution, there was minimal change between the two samples. These findings suggest that the increase in flow stress due to the solid-solution strengthening by hydrogen is a root cause of accelerated deformation twinning at a smaller strain, leading to an enhanced work-hardening rate and improved uniform elongation.
C alloy measured in the electrostatic levitation furnace onboard the international space station石川 毅彦*; 織田 裕久*; 小山 千尋*; 下西 里奈*; 池内 留美子*; Paradis, P.-F.*; 岡田 純平*; 福山 博之*; 山野 秀将
International Journal of Microgravity Science and Application, 42(2), p.420202_1 - 420202_10, 2025/04
Samples of stainless steel (SS) - boron carbide (BC) alloys were levitated in the Electrostatic Levitation Furnace onboard the International Space Station (ISS-ELF) to measure the thermophysical properties of their melts. Melting of samples of two different compositions (SS-12.3, and 28 mass% BC) were attempted in the furnace. Even though only one sample (SS-12.3 mass% BC) could be melted, its density was successfully obtained.
櫻井 惇也*; 鳥形 啓輔*; 松永 学*; 高梨 直人*; 日比野 真也*; 木津 健一*; 森田 聡*; 井元 雅弘*; 下畠 伸朗*; 豊田 晃大; et al.
鉄と鋼, 111(5), p.246 - 262, 2025/04
被引用回数：1 パーセンタイル：26.96(Metallurgy & Metallurgical Engineering)Creep testing is time-consuming and costly, leading institutions to limit the number of tests conducted to the minimum necessary for their specific objectives. By pooling data from each institution, it is anticipated that predictive models can be developed for a wide range of materials, including welded joints and degraded materials exposed to service conditions. However, the data obtained by each institution is often highly confidential, making it challenging to share with others. Federated learning, a type of privacy-preserving computation technology, allows for learning while keeping data confidential. Utilizing this approach, it is possible to develop creep life prediction models by leveraging data from various institutions. In this paper, we constructed global deep neural network models for predicting creep rupture life of heat-resistant ferritic steels in collaboration with eight institutions using the federated learning system we developed for this purpose. Each institution built a local model using only its own data for comparison. While these local models demonstrated good predictive accuracy for their respective datasets, their predictive performance declined when applied to data from other institutions. In contrast, the global model constructed using federated learning showed reasonably good predictive performance across all institutions. The distance between each institution's data was defined in the space of explanatory variables, with the NIMS data, which had the largest dataset, serving as the reference point. The global model maintained high predictive accuracy regardless of the distance from the NIMS data, whereas the predictive accuracy of the NIMS local model significantly decreased as the distance increased.
永田 寛; 河内山 真美; 茅根 麻里奈; 菅谷 直人; 西村 嵐; 石川 譲二; 坂井 章浩; 井手 広史
JAEA-Data/Code 2024-016, 44 Pages, 2025/03
JAEA-Data-Code-2024-016.pdf:3.54MB
原子炉施設の構造材の元素組成は、廃止措置計画の策定などの際に評価を行う放射化計算において、重要なパラメータの一つとして使用されている。このうち、試験研究炉の構造材として使用されているアルミニウム合金などの元素組成については、主要成分以外の元素については十分なデータが得られていない。このことから、材料試験炉「JMTR」の主要な構造材として使用されてきたアルミニウム合金、ベリリウム、ハフニウムなどから試料を採取し、元素組成の分析を実施した。本報告書は、令和5年度に取得した78元素の元素組成データについてまとめたものである。
neutron diffraction measurement during tensile deformation山下 享介*; 諸岡 聡; Gong, W.; 川崎 卓郎; Harjo, S.; 北條 智彦*; 興津 貴隆*; 藤井 英俊*
ISIJ International, 64(14), p.2051 - 2060, 2024/12
被引用回数：1 パーセンタイル：9.99(Metallurgy & Metallurgical Engineering)An Fe-0.15C-5Mn-0.5Si-0.05Nb steel annealed at 660C and 685C showed L
ders deformation followed by high work hardening, with variations in Lders strain and hardening behavior. neutron diffraction during tensile tests analyzed phase stresses, strength contributions, and austenite orientation. Deformation-induced martensite contributed 
1000 MPa to strength near tensile failure, while austenite mainly enhanced ductility via transformation-induced plasticity. Austenite transformed to martensite during Lders deformation regardless of orientation, though 311-oriented grains tended to remain along the tensile direction.
