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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：0 パーセンタイル：0.00(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.
岡田 和歩*; 柴田 曉伸*; 木村 勇次*; 山口 正剛; 海老原 健一; 辻 伸泰*
Acta Materialia, 280, p.120288_1 - 120288_14, 2024/11
被引用回数：1 パーセンタイル：0.00(Materials Science, Multidisciplinary)The present study aimed at strengthening prior austenite grain boundary (PAGB) cohesive energy using carbon segregation and investigated the effect of carbon segregation at PAGB on the microscopic crack propagation behavior of hydrogen-related intergranular fractures in high-strength martensitic steels. At the low hydrogen content (below 0.2 wt. ppm), the fracture initiation toughness (
) and tearing modulus (
), corresponding to crack growth resistance, were significantly improved by carbon segregation. In contrast, and did not change by carbon segregation at the high hydrogen content (above 0.5 wt. ppm). Considering the non-linear relationship between the toughness properties and the PAGB cohesive energy, the experimentally evaluated toughness properties ( and ) and the GB cohesive energy previously calculated by first-principles calculations were semi-quantitatively consistent even at the high hydrogen content. The microstructure observation confirmed that the plastic deformation associated with crack propagation, such as the local ductile fracture of uncracked ligaments and the formation of dislocation cell structures/nano-voids, played an important role in the non-linear relationship between the toughness properties and PAGB cohesive energy.
neutron diffraction study to elucidate hydrogen effect on the deformation mechanism in Type 310S austenitic stainless steel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.
Proceedings of the 7th International Symposium on Steel Science (ISSS 2024), p.237 - 240, 2024/11
Hydrogen embrittlement has long been an obstacle to the development of safe infrastructure. However, in contrast to hydrogen's embrittling effect, recent research has revealed that the addition of hydrogen improves both the strength and uniform elongation of AISI Type 310S austenitic stainless steel. A detailed understanding of how hydrogen affects the deformation mechanism of this steel could pave the way for the development of more advanced materials with superior properties. In the present study, neutron diffraction experiments were conducted on Type 310S steel with and without hydrogen-charged to investigate the effect of hydrogen on the deformation mechanism. In addition to the effect of solid-solution strengthening by hydrogen, the q-value, a parameter representing the proportion of edge and screw dislocations in the accumulated dislocations, was quantitatively evaluated using CMWP analysis on neutron diffraction patterns. The comparison of q-values between the hydrogen-charged and non-charged samples reveals that hydrogen has minimal effect on dislocation character in Type 310S steel.
岡田 和歩*; 柴田 曉伸*; Gong, W.; 辻 伸泰*
Acta Materialia, 225, p.117549_1 - 117549_13, 2022/02
被引用回数：29 パーセンタイル：91.89(Materials Science, Multidisciplinary)In this study, the deformation microstructure of hydrogen-charged ferritic-pearlitic 2Mn-0.1C steel was characterized using SEM-BSE, SEM-EBSD, TEM, and neutron diffraction. The microscopic mechanism of hydrogen-related quasi-cleavage fracture along the 
planes was also discussed. It was found that hydrogen increased the relative velocity of screw dislocations to edge dislocations, leading to a tangled dislocation morphology, even at the initial stage of deformation (strain = 0.03). In addition, the density of screw dislocations at the later stage of deformation (strain = 0.20) increased in the presence of hydrogen. Based on the experimental results, it is proposed that a high density of vacancies accumulated along slip planes by jog-dragging of screw dislocations, and coalescence of the accumulated vacancies led to the hydrogen-related quasi-cleavage fracture along the {011} slip planes.
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.
no journal, ,
近年、高圧ガス環境中で均一に水素を固溶させたオーステナイト系ステンレス鋼SUS310Sにおいて、強度・延性が共に向上することが報告された。これは水素による固溶強化と双晶変形の促進によると説明されているが、転位密度や積層欠陥など、個々の因子に対する水素の影響の詳細は明らかとなっていない。本研究では、J-PARCの工学材料回折装置「匠」での引張試験中その場中性子回折により、変形メカニズムを明らかにすることを試みた。得られた中性子回折パターンから、水素による体積変化や固溶強化の存在を確認した。更に、転位密度、積層欠陥密度、双晶変形開始ひずみ・応力を評価した。これらの解析により、水素が変形メカニズムに与える影響を明らかにした。
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.
no journal, ,
Hydrogen is being considered as an alternative energy carrier to fossil fuels to achieve the goal of Carbon Neutrality. While hydrogen has historically been associated with causing steel embrittlement, Ogawa et al. reported that the introduction of hydrogen to a Fe-24Cr-19Ni-based (mass%) austenitic stainless steel (AISI Type 310S) enhances both strength and ductility, thus counteracts the embrittlement effect. Although this phenomenon was qualitatively explained by the hydrogen-induced solid-solution strengthening and the promotion of deformation twinning, the influence of hydrogen on the development of dislocations and stacking faults (, twin nuclei) during deformation remains less understood. The aim of this work is to investigate the effects of hydrogen on the evolution of these crystal defects and overall deformation mechanisms by using neutron diffraction measurements.
伊東 達矢; 小川 祐平*; Gong, W.; 川崎 卓郎; 岡田 和歩*; 柴田 曉伸*; Harjo, S.
no journal, ,
近年、水素添加によりSUS310Sの強度と延性が共に向上することが報告された。本研究では、「匠」を利用した引張試験中その場中性子回折実験を行い、転位密度や積層欠陥密度など、個々の因子に対する水素の影響を定量的に解明することを試みた。
伊東 達矢; 小川 祐平*; Gong, W.; 川崎 卓郎; 岡田 和歩*; 柴田 曉伸*; Harjo, S.
no journal, ,
Hydrogen is attracting attention as an alternative energy carrier to fossil fuels to establish a sustainable society. However, hydrogen is considered to cause embrittlement in steel, which has been a longstanding issue known as hydrogen embrittlement. In contrast to the embrittlement, recently, Ogawa 
, reported that the addition of hydrogen improved both strength and ductility in SUS310S (Fe-24Cr-19Ni mass%) steel. This phenomenon is attributed to hydrogen-induced solid solution strengthening and the promotion of twinning deformation. These approaches are gaining attention as effective ways to utilize hydrogen, which has long been considered harmful. However, the impact of hydrogen on crystal defects (dislocations, stacking faults) and the mechanisms behind enhanced twinning in SUS310S steel remain unclear. In this work, we investigated the deformation mechanisms of hydrogen-charged SUS310S steel by neutron diffraction measurement conducted by TAKUMI (MLF-BL19) of J-PARC.
伊東 達矢; 小川 祐平*; Gong, W.; 川崎 卓郎; 岡田 和歩*; 柴田 曉伸*; Harjo, S.
no journal, ,
持続可能な社会の構築に向け、国を挙げて水素社会の実現に向けた研究が行われている。水素インフラを構築するために、水素環境で強度・延性に優れる鉄鋼材料が求められているが、一般的に水素は脆化を引き起こすと考えられてきた。しかし近年、SUS310S (Fe-24Cr-19Ni (mass%))において、水素により強度・延性が共に向上することが報告され、注目を集めている。これには水素由来の固溶強化と双晶変形の促進が寄与していると考えられているが、転位密度や積層欠陥など、個々の因子に対する水素の影響の詳細は明らかとなっていない。そこで本研究では、MLFの工学材料回折装置 「匠」を利用した引張変形中その場中性子回折実験を行い、変形メカニズムに及ぼす水素の影響を定量的に評価した。
伊東 達矢; 小川 祐平*; Gong, W.; 川崎 卓郎; 岡田 和歩*; 柴田 曉伸*; Harjo, S.
no journal, ,
持続可能な社会の構築に向け、国を挙げて水素社会の実現を目指した研究が行われている。水素社会を実現するためには、安全性と信頼性を両立した水素インフラの構築が必要不可欠であり、そこで用いられる鉄鋼材料の変形メカニズムに対する水素の影響を明らかにすることは極めて重要である。多くの場合、水素は鉄鋼材料を脆化させ、機械特性を低下させると考えられてきた。しかし近年、小川らにより、SUS310S(Fe-24Cr-19Ni, mass%)に水素を均一に添加することで強度・延性が共に向上することが報告された)。これは、これまで材料特性を悪化させると考えられてきた水素を有効利用することが出来る手法として、注目を集めている。これには、水素由来の固溶強化と双晶変形の促進が寄与していると考えられている。しかし、転位密度や積層欠陥密度など、材料特性を司る個々の因子に対する水素の影響の詳細は明らかになっていない。そこで本研究では水素チャージを施したSUS310Sに対して「匠」を用いた引張試験中その場中性子回折実験を行い、変形メカニズムに及ぼす固溶水素の影響を調査した。
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.
no journal, ,
カーボンニュートラルの実現のため、水素は化石燃料を代替するエネルギーキャリアとして注目を集めている。歴史的に水素は鉄鋼材料の脆化を引き起こすとされてきたが、小川らはSUS310Sに水素を添加することで強度と延性が共に向上することを報告した。これらは水素による固溶強化と双晶変形の促進によると定性的に説明されているが、変形中の転位や積層欠陥の発達に対して、水素がどのような影響を与えるかその詳細は明らかとなっていない。本研究は、その場中性子回折により、これらの欠陥に対する水素の影響を明らかにすることを目的とする。
