Role of solute hydrogen on mechanical property enhancement in Fe-24Cr-19Ni austenitic steel; An 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

https://doi.org/10.1016/j.actamat.2025.120767

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.

Crystal structures of ReO under hydrostatic pressure; A Combined neutron, X-ray, Raman, and first-principles calculation study

Efthimiopoulos, I.*; Klotz, S.*; Kunc, K.*; Baptiste, B.*; Chauvigne, P.*; 服部 高典

Physical Review B, 111(13), p.134103_1 - 134103_13, 2025/04

https://doi.org/10.1103/PhysRevB.111.134103

X線回折、中性子回折、ラマン散乱、第一原理計算を用いて、ReOの高圧力下での挙動を15GPaまで包括的に調べた。常圧=3構造は0.7GPaで空間群=3の立方晶相に連続的に相転移し、その後少なくとも15GPaまで安定であることがわかった。過去この圧力領域で報告されていた単斜晶構造や菱面体晶=3構造への転移は、試料に高輝度放射光X線を照射したことによる試料の劣化によるものであり、人工的なものであることが分かった。また今回、=3相の構造の圧力依存性と正確な状態方程式および天然試料と同位体濃縮O試料のラマン散乱データを示した。このデータから、リジッドなReO八面体が圧力とともに回転することによって、相転移および高密度化が起こることが分かった。

Solid-state Alder-ene reaction of 1-hexene under high pressure

Xu, J.*; Lang, P.*; Liang, S.*; Zhang, J.*; Fei, Y.*; Wang, Y.*; Gao, D.*; 服部 高典; 阿部 淳*; Dong, X.*; et al.

Journal of Physical Chemistry Letters (Internet), p.2445 - 2451, 2025/00

https://doi.org/10.1021/acs.jpclett.4c03696

アルダー-エン反応は、アルケンとアリル水素との化学反応であり、C-C結合を構築する効率的な方法である。従来、この反応には触媒、高温、あるいは光触媒が必要であった。本研究では、触媒を用いずに室温下で加圧することで成功した1-ヘキセンのアルダー-エン反応を報告する。1-ヘキセンは4.3GPaで結晶化し、18GPaで重合してオレフィンを形成する。ガスクロマトグラフィー-質量分析法により、1-ヘキセンが高圧下でのアルダー-エン反応により二量体を生成することを発見した。その場中性子回折から、この反応過程はトポケミカル則に従わないことがわかった。理論計算により、1つのC-H 結合と2つのアルケン結合を含む6員環遷移状態が示され、そのエネルギーは20GPaまで圧縮すると明らかに減少した。本研究は、触媒を用いずに室温でアルダー-エン反応を実現する新規かつ有望な方法を提供し、この重要な反応の応用を拡大するものである。

令和3・4年度JRR-3中性子ビーム利用における独自利用研究・技術開発報告

物質科学研究センター

JAEA-Review 2024-037, 141 Pages, 2024/11

JAEA-Review-2024-037.pdf:13.08MB

JRR-3(Japan Research Reactor No.3)には、日本原子力研究開発機構(原子力機構)が所管する15台の中性子ビーム利用実験装置が設置されており、装置高度化を含めた原子力機構の独自利用を行うとともに施設供用装置として外部利用者に供し、様々な研究成果を創出している。本報告書は、運転再開後の令和3年度、令和4年度の独自利用研究および中性子ビーム利用実験装置の高度化などの技術開発の進捗状況を取りまとめたものである。

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

https://doi.org/10.2355/isijisss.2024.0_237

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.

Pearlite growth kinetics in Fe-C-Mn eutectoid steels; Quantitative evaluation of energy dissipation at pearlite growth front via experimental approaches

Zhang, Y.-J.*; 梅田 岳昌*; 諸岡 聡; Harjo, S.; 宮本 吾郎*; 古原 忠*

Metallurgical and Materials Transactions A, 55(10), p.3921 - 3936, 2024/10

https://doi.org/10.1007/s11661-024-07518-1

In this study, a series of eutectoid steels with Mn addition up to 2 mass% were isothermally transformed at various temperatures from 873 K to 973 K to clarify the pearlite growth kinetics and the underlying thermodynamics at its growth front. The microscopic observation indicates the acceleration in pearlite growth rate and refinement in lamellar spacing by decreasing the transformation temperature or the amount of Mn addition. After analyzing the solute distribution at pearlite growth front via three-dimensional atom probe, no macroscopic Mn partitioning across pearlite/austenite interface is detected, whereas Mn segregation is only observed at ferrite/austenite interface. Furthermore, in-situ neutron diffraction measurements performed at elevated temperatures reveals that the magnitude of elastic strain generated during pearlite transformation is very small.

Anomalous dislocation response to deformation strain in CrFeCoNiPd high-entropy alloys with nanoscale chemical fluctuations

Ying, H.*; Yang, X.*; He, H.*; Yan, A.*; An, K.*; Ke, Y.*; Wu, Z.*; Tang, S.*; Zhang, Z.*; Dong, H.*; et al.

Scripta Materialia, 250, p.116181_1 - 116181_7, 2024/09

https://doi.org/10.1016/j.scriptamat.2024.116181

Nanoscale chemical fluctuations and their effect on the deformation behavior of CrFeCoNi-based high-entropy alloys (HEAs) were investigated using small-angle scattering and in situ neutron diffraction measurements. Small-angle scattering results demonstrated the presence of nano (10 nm) chemical fluctuations in the as-prepared CrFeCoNiPd HEAs, which was attributed to the negative mixing of enthalpy and the significant atomic radius difference between Pd and the constituent elements in the CrFeCoNi-based alloys. Subsequent tensile tests demonstrated that the yield and tensile strengths of the as-prepared CrFeCoNiPd HEA surpass those of the as-prepared CrMnFeCoNi HEA. Neutron diffraction data analysis revealed an anomalous response of dislocation evolution with the strain.

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

松下 慧*; 土田 紀之*; 石丸 詠一郎*; 平川 直樹*; 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

This study investigated the anisotropy of the tensile properties in a duplex stainless steel of 24Cr-5Ni-0.18N based on in situ neutron diffraction experiments. The 24Cr-5Ni-0.18N steel showed a better balance of tensile strength (TS) and uniform elongation (U.El) compared with 329J4L and 329J1 steels. The Lankford value (-value) of the 24Cr-5Ni-0.18N steel was comparable to other duplex stainless steels while showing a larger TS. Regarding the anisotropy of the mechanical properties, the results for a test specimen oriented at 45 showed a low yield strength (YS) and TS, but a better U.El and -value. The neutron diffraction results are discussed to explain the mechanical properties.

マルチモーダル化したマグネシウム合金の変形中の構成相・組織の挙動

Harjo, S.; Gong, W.; 相澤 一也; 山崎 倫昭*; 川崎 卓郎

日本材料学会第58回X線材料強度に関するシンポジウム講演論文集, p.58 - 60, 2024/07

The experiment and analysis procedures for a sample exhibiting multimodal structures were outlined. The sample, a MgZnY alloy, initially comprised two phases: the HCP matrix (Mg) and the long-period stacking ordered phase (LPSO), constituting approximately 25% of the volume. Through hot extrusion at 623 K with an extrusion ratio (R) of 5.0, the alloy was rendered multimodal. Specifically, at an R value of 5.0, dynamic recrystallization occurred partially within the Mg phase, resulting in a bimodal microstructure. This microstructure consisted of a deformed Mg component and a recrystallized Mg component. An analysis employing Electron Backscatter Diffraction (EBSD) data facilitated multimodal characterization, enabling successful determination of stresses within the individual Mg components, as well as the LPSO phase stress.

変形その場パルス中性子回折実験により高強度マグネシウム合金の強度増加機構を解明

Harjo, S.

Isotope News, (793), p.13 - 16, 2024/06

高強度マグネシウム(Mg)合金の高温押出加工による大幅な強度増加の機構を引張変形その場中性子回折実験によってどのように解明したかについて紹介する。高温押出加工の条件により組織が複雑化し、構成相それぞれの組織からの強度への寄与について解説する。