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小林 大輝*; 小松 一生*; 伊藤 颯*; 町田 真一*; 服部 高典; 鍵 裕之*
Journal of Physical Chemistry C, 130(25), p.8795 - 8805, 2026/06
被引用回数：0氷IVは、氷の高圧下における準安定相であり、水から結晶化することは極めて稀であるため、「ウィル・オ・ザ・ウィスプ(幻灯)」という愛称で呼ばれており、これは氷の不安定で幽霊のような形態を表している。本研究では、水-油エマルジョンを用いた実験により、0.45GPaから1.1GPaの圧力下において、液体の水が均一核生成温度(
)で再現性よく、かつ選択的に氷IVへと結晶化することを報告する。圧力による氷Ihの融解とそれに続く再結晶化を追跡することで、以下であっても液体の水が優先的に氷IVへと結晶化することを示した。乳化氷試料における高い静水圧状態と結晶成長の抑制により、中性子回折法を用いて氷IVおよびその潜在的な水素配列状態の両方について、信頼性の高い構造解析を行うことができた。実験で達成可能な配列度は極めて低く、結晶化方法にほとんど依存しなかった。
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
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.
Harjo, S.
金属, 96(5), p.354 - 360, 2026/05
金属材料の変形や組織変化の理解には、応力-ひずみ曲線などのマクロ特性と、結晶構造や相分率、格子ひずみ、転位といったミクロ情報の統合評価が重要である。本稿では中性子回折その場測定の有効性を概説した。TOF法により変形・熱処理中の相分率や格子ひずみ、欠陥を同時に取得でき、力学応答との対応付けが可能となる。さらにFe-18Ni合金と超微細粒SUS304を例に、その有効性を示した。
-iron at high pressures determined using neutron diffraction青木 勝敏*; 高野 将大*; 福山 鴻*; 鍵 裕之*; 町田 晃彦*; 齋藤 寛之*; 服部 高典; 佐野 亜沙美; 舟越 賢一*
Physical Review B, 113(18), p.184440_1 - 184440_6, 2026/05
被引用回数：1 パーセンタイル：86.01(Materials Science, Multidisciplinary)体心立方(bcc)-鉄の磁気モーメントの温度依存性をその場中性子粉末回折法を用いて、約2GPaおよび6GPaの圧力下で300
950Kの範囲において調べた。磁気散乱の相対寄与を高めるため、中性子散乱長が天然Feの約半分である
Fe同位体が用いられた。キュリー温度(
)は、2.1GPa, 6.0GPa, 6.7GPaでそれぞれ946(30)K、838(50)K、740(40)Kと決定され、(K) = 1043 - 49(7)
+ 1.3(1.2)
で表される磁気相境界が決定された。6.7GPaで加熱すると、磁気転移に続いて
構造転移が観測された。この結果は、磁気相境界が相境界の低温側に位置することを示している。したがって、転移は、常磁性bcc鉄から常磁性fcc鉄への構造変化に対応する。
neutron diffraction mapping measurement山下 享介*; 柳樂 知也*; Gong, W.; 川崎 卓郎; Harjo, S.; 潮田 浩作*; 藤井 英俊*
ISIJ International, 66(5), p.673 - 684, 2026/04
被引用回数：0 パーセンタイル：0.00(Metallurgy & Metallurgical Engineering)In this study, neutron diffraction mapping was performed on linear friction welded (LFW) joints of 12 mm thick high-phosphorus weathering steel (SPA-H) to evaluate residual stress, dislocation density, and crystallographic orientation. Welding was conducted under applied pressures of 100 and 250 MPa. The weld interface mainly consisted of refined ferrite with minor retained austenite and martensite, indicating reverse transformation to austenite during welding. The 250 MPa condition resulted in a lower welding temperature. Elongated grains were observed near the surface along the oscillation direction, while equiaxed grains appeared at the center. Both joints showed high tensile residual stresses at the weld center and compressive stresses near the surface. Higher applied pressure increased dislocation density because of suppressed dynamic recovery. Strong texture formation due to plastic flow was observed, while the effect of applied pressure on texture development was limited.
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.
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：4 パーセンタイル：64.95(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.
neutron diffraction at cryogenic temperatures山下 享介*; Harjo, S.; Gong, W.; 川崎 卓郎; 森戸 茂一*; 諸岡 聡; 藤井 英俊*; 友田 陽*
Journal of Alloys and Compounds, 1056, p.186668_1 - 186668_11, 2026/02
In this study, neutron diffraction during cryogenic cooling was performed on Fe-31Ni-10Co-3Ti alloy to investigate changes in the austenite lattice constant and martensite tetragonality during thin-plate martensitic transformation. The austenite lattice constant showed only a slight change because of the Invar effect, but decreased below the Ms temperature due to elastic accommodation of transformation strain. Broadening of austenite diffraction peaks and EBSD analysis indicated localized plastic accommodation near intersecting martensite regions. For martensite, the a-axis decreased while the c-axis increased anomalously with decreasing temperature, leading to enhanced tetragonality below 35 K. During heating, the c-axis decreased and tetragonality was reduced. These behaviors are attributed to Bain strain during twin formation and possible interfacial stress with surrounding austenite.
Cho, K.*; 山下 葵平*; 角谷 心之輔*; 齊藤 拓馬*; 佐々木 泰祐*; 澤泉 克彦*; 奥川 将行*; 小泉 雄一郎*; 眞山 剛*; 菊川 泰地*; et al.
Acta Materialia, 303, p.121696_1 - 121696_18, 2026/01
被引用回数：7 パーセンタイル：80.50(Materials Science, Multidisciplinary)The deformation behavior and strengthening mechanism of Inconel 718 with a hierarchical structure composed of microscale crystallographic lamellar microstructure (CLM) and nanoscale cellular structure, fabricated by laser powder bed fusion, were clarified via nanoscale microstructural and in-situ neutron diffraction analyses. The CLM is a layered structure parallel to the building direction (BD) and consists of relatively wide main and narrow sub-layers with 110 and 100 orientations, respectively, with respect to BD. This is the first study to demonstrate that the yield stress of the alloys depends strongly on deformation stresses of the sub-layers, even though Schmid factors of the primary slip system for both layers are the same. The sub-layer continues to deform elastically even beyond the micro-yield point of the main layer, which results in the macroscopic strengthening at an early stage of deformation. On the other hand, the cellular structure is formed in both layers, associated with a dendritic cell growth along 100 direction, Nb segregation between the cells and an accumulation of dislocations to decrease a residual stress. The cell boundaries with numerous dislocations and Nb segregation act as a strong barrier to dislocation motion resulting in a stress increase through the Hall-Petch law, even though they are low-angle grain boundaries. The spacing and morphology of the cell boundary depend strongly on fabrication conditions. The optimized cellular structure provides significant strengthening comparable to or greater than that caused by large-angle grain boundaries, thereby increasing the macroscopic strength of the alloys through hardening of the sub-layer.
Zhu, L.*; Dong, W.*; Naeem, M.*; Kong, H.*; Hu, C.*; Fan, Z.*; Gong, W.; Harjo, S.; Lan, S.*; Wu, Y.*; et al.
Acta Materialia, 303, p.121734_1 - 121734_10, 2026/01
被引用回数：3 パーセンタイル：51.29(Materials Science, Multidisciplinary)Body-centered cubic (BCC) metals typically exhibit high yield strength but limited work hardening and uniform elongation, especially at low temperatures. High-entropy alloys (HEAs) offer opportunities to overcome these limitations, though their deformation mechanisms remain unclear. Using in situ neutron diffraction and microstructural analysis, this study identifies the origin of the exceptionally large uniform elongation at liquid nitrogen temperature in a single-phase BCC (TiZrHf)
Al
Nb
HEA. Initial plastic deformation is governed by a BCC-to-orthorhombic (") transformation, followed by " twinning and deformation-induced amorphization at later stages. The cooperation of these mechanisms suppresses work softening from dislocation plasticity, enabling high yield strength with large uniform elongation and providing a viable strategy for designing cryogenic structural materials.
and L1 phase in deformation behaviors of additively manufactured FeCrNiAlTi alloyWang, X.*; Wang, Y.*; Gong, W.; Wu, W.*; Zhang, Y.*; Harjo, S.; Yang, Z.*; Chen, H.*
International Journal of Plasticity, 195, p.104502_1 - 104502_16, 2025/12
Precipitation hardening strengthens FCC alloys but often reduces ductility. This study shows that precipitates can also modify deformation behavior to mitigate this trade-off. An FeCrNiAlTi FCC alloy fabricated by laser additive manufacturing contains incoherent L2 precipitates at cell walls and coherent L1 precipitates within cells. By controlling precipitation, an excellent strength-ductility balance was achieved at both ambient and cryogenic temperatures. High-density precipitates provide strengthening while promoting deformation-induced stacking faults and twinning, thereby enhancing work hardening via strain heterogeneity. In situ neutron diffraction indicates that post-yield lattice strain governs stacking fault and twin formation. Simulations show that interfacial misfit of the L2 phase and the size and spacing of the L1 phase amplify local strain.
山下 享介*; 柳樂 知也*; Gong, W.; 川崎 卓郎; Harjo, S.; 潮田 浩作*; 藤井 英俊*
鉄と鋼, 111(17), p.1057 - 1071, 2025/12
Neutron diffraction mapping was conducted on linear friction welded joints of 12 mm thick high-phosphorus weathering steel (SPA-H) to evaluate residual stress, dislocation density, and crystallographic orientation. Welding was performed at 100 MPa and 250 MPa. The weld interface mainly comprised refined ferrite with retained austenite and martensite, indicating temperatures exceeded A1 and induced reverse transformation. The 250 MPa joint showed a lower welding temperature. Elongated grains formed near the surface along the oscillation direction (OD), while equiaxed grains appeared at the center. High tensile residual stresses were found at the weld center, with compressive stress near the surface perpendicular to the weld. Pressure had little effect on overall stress trends. Dislocation density increased with pressure due to suppressed dynamic recovery. Strong texture developed at the interface, with limited pressure dependence.
Jing, Z.*; 山口 敏男*; 町田 真一*; 服部 高典; Zhou, Y.*
Journal of Chemical Physics, 163(19), p.194505_1 - 194505_12, 2025/11
被引用回数：0 パーセンタイル：0.00(Chemistry, Physical)ギガパスカル(GPa)範囲の圧力におけるイオンの溶媒和は、高圧化学合成および地球内部における物質循環にとって極めて重要である。我々は、0.1MPaおよび0.7GPa/298KにおけるMCl (M = Li, Na, K, Rb, Cs)の重水素化水溶液について、中性子散乱(NS)実験および分子動力学(MD)シミュレーションを実施した。経験的ポテンシャル構造精密化(EPSR)手法を用いてNSデータを分析した。0.7GPaへの圧縮に伴い、外殻水分子がイオンの最近接原子殻に入り込み、溶媒和イオンクラスターは高密度化する。第一溶媒和殻における水分子双極子の配向分布に基づく水和因子
と静的水和数
は、圧縮がイオンの水和能力を弱めることを示す。圧縮はイオン拡散、特に構造破壊イオンの拡散を抑制する。イオン拡散係数
、水分子滞留時間
、動的水和数
は、高圧下でRb
とCsが構造形成イオンの特性を示すことを示す。動的特性は静的構造よりも圧力に敏感である。
Gu, G. H.*; Ha, H.*; Harjo, S.; Gong, W.; Louzguine-Luzgin, D. V.*; Kim, H. S.*
Materials Science & Engineering A, 943, p.148818_1 - 148818_10, 2025/10
High-strength structural alloys are essential for advanced engineering. This study explores the mechanical behavior of a dual-phase AlCoNiV medium-entropy alloy (MEA) with FCC and BCC phases. The alloy shows excellent performance, with a yield strength of 1148 MPa, tensile strength of 1556 MPa, and 40% uniform elongation. In-situ neutron diffraction and EBSD analyses reveal that strength originates from the intrinsic responses of both phases. The BCC phase carries more load, while dislocation buildup at phase boundaries enhances strength via hetero-deformation-induced (HDI) strengthening. Synergistic effects, including stress partitioning and load redistribution, further improve mechanical performance. These findings highlight the role of phase-specific properties and interphase interactions in alloy robustness and offer insights for microstructural optimization.
Jeong, S. G.*; Kwon, J.*; Kim, E. S.*; Prasad, K.*; Harjo, S.; Gong, W.; 川崎 卓郎; Estrin, Y.*; Bouaziz, O.*; Hong, S. I.*; et al.
Materials Science & Engineering A, 942, p.148712_1 - 148712_11, 2025/10
被引用回数：2 パーセンタイル：51.29(Nanoscience & Nanotechnology)The cellular structure plays a key role in determining the mechanical properties of metal additive manufacturing (MAM) components. This study presents in situ neutron diffraction and dislocation density-based modeling for a CoCrFeMnNi high-entropy alloy (HEA) made via directed energy deposition (DED). A constitutive model based on the Kocks-Mecking-Estrin framework was used to represent the cellular structure. Parametric analysis showed lower dislocation accumulation and annihilation rates in the as-built sample (with cellular structure) than in the heat-treated one. These differences are linked to dislocation forest networks and local stacking fault energy variations. Dislocation density across cell interiors and walls was also compared with deformation-induced dislocation cells.
neutron diffractionLiu, Y.*; Yan, Z.*; Gao, Y.*; Li, Y.*; Gan, B.*; Harjo, S.; Gong, W.; 川崎 卓郎; Li, S.*; Wang, Y.-D.*
Microstructures (Internet), 5(4), p.2025096_1 - 2025096_15, 2025/10
The micromechanical behaviors and dislocation evolution in a polycrystalline Ni-Co-based superalloy were systematically investigated by neutron diffraction tensile testing combined with line profile analysis. The results reveal the sequential activation of ' shearing and Orowan looping mechanisms, with interphase load partitioning governed by strain-dependent interactions of dislocation and precipitate. During the initial plastic deformation, the and ' phases undergo co-deformation through dislocation shearing without load transfer, while the Orowan looping facilitates the load transfer from to ' phase at a higher strain level. Furthermore, the low stacking fault energy leads to a rising fraction of screw dislocations by suppressing cross-slip. Crucially, the pinning effect of ' precipitates hinders the rearrangement of these dislocations into low-energy structures, resulting in the formation of high-energy, weakly screened dislocation configurations. These findings provide new evidence for the planar slip dominance in Ni-Co-based superalloys, enabling quantitative assessment of microstructural evolution and micromechanical responses.
齊藤 寛之*; 町田 晃彦*; 服部 高典; 佐野 亜沙美; 舟越 賢一*; 佐藤 豊人*; 折茂 慎一*; 青木 勝敏*
Physica B; Condensed Matter, 714, p.417234_1 - 417234_3, 2025/10
被引用回数：0 パーセンタイル：0.00(Physics, Condensed Matter)「高温高圧下における重水素化ニッケルの重水素組成に関する中性子回折研究[Phys. B Condens. Matter. 587 (2020) 412153]」の正誤表を記した。
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：64.95(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.
高梨 美咲*; 日高 僚太*; 大久保 亘太*; 増村 拓朗*; 土山 聡宏*; 諸岡 聡; 前田 拓也*; 中村 修一*; 植森 龍治*
ISIJ International, 65(9), p.1384 - 1393, 2025/08
被引用回数：1 パーセンタイル：30.65(Metallurgy & Metallurgical Engineering)This study investigates the strengthening mechanism of ausforming in martensitic steels, focusing on the role of dislocation inheritance from austenite. By analyzing Fe-5%Mn-C alloys, the researchers quantified dislocation densities before and after ausforming and examined how carbon content affects hardening. Results show that both hardness and dislocation density of ausformed martensite increase with greater deformation in austenite and higher carbon content. The findings support that ausforming strengthens martensite through dislocation accumulation, consistent with the Bailey-Hirsch relationship. 
neutron diffraction revealed that dislocation inheritance occurs only in steels with sufficient carbon, while additional dislocations are introduced during martensitic transformation.
