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Zhang, Y.*; 丸澤 賢人*; 工藤 航平*; 諸岡 聡; Gong, W.; Harjo, S.; 宮本 吾郎*; 古原 忠*
Journal of Materials Science & Technology, 275, p.250 - 259, 2026/12
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)This study examines how substitutional alloying elements (Mn, Cr, Al, and Si) influence low-temperature tempering reactions in high carbon martensitic steels. Through comprehensive experimental techniques including 
neutron diffraction et al., the work clarifies how alloying modifies tempering kinetics by affecting carbon diffusion and phase nucleation. Al and Cr strongly suppress martensite tetragonality reduction and carbon redistribution, while retained austenite decomposes in two stages that are selectively delayed by different alloying elements. Overall, the tempering sequence and kinetics are shown to be governed by alloying-dependent control of carbon mobility and phase transformations.
Tong, Z.*; Xia, C.*; Li, W.*; Ding, W.*; Guo, B.*; Min, N.*; Gong, W.; Harjo, S.; 辻 伸泰*
Journal of Materials Science & Technology, 266, p.127 - 140, 2026/09
被引用回数：0 パーセンタイル：0.00(Materials Science, Multidisciplinary)This study elucidates the mechanism of post-deformation ferrite transformation during relaxation and demonstrates that controlling ferrite grain size and volume fraction enhances the strength-ductility balance of low-carbon martensitic steel. In situ neutron diffraction and microscopy show that austenite-to-ferrite transformation preferentially occurs at grain boundaries due to localized dislocation accumulation. Dislocation density remains elevated during relaxation at 755 
C but fully recovers at 765 C. Thermodynamic analysis indicates that transformation behavior is governed by the combined effects of chemical driving force and stored dislocations, enabling precise control of ferrite microstructure. Exploiting grain-boundary transformation heterogeneity through controlled relaxation provides an effective strategy to overcome the strength-ductility trade-off in high-strength martensitic steels.
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.
Zhou, D.*; Zhang, X.*; Pang, X.*; Zhao, Z.*; Chen, X.*; Wei, S.*; Yang, C.*; Gong, W.; Harjo, S.; Li, R.*; et al.
Materials Research Letters (Internet), 14(6), p.689 - 698, 2026/06
被引用回数：1 パーセンタイル：0.00(Materials Science, Multidisciplinary)Here, we investigated the room-temperature (298 K) and cryogenic-temperature (77 K) mechanical behaviors of binary Al-Mg alloys over a wide range of Mg concentrations (2.8-13.1 at.%). A ductile-to-brittle transition was observed at 77 K as the Mg content increased from 7.5 to 13.1 at.%, accompanied by a significant decrease in impact energy from 161 J to 14 J. Through detailed theoretical calculations and experimental observations, this composition-dependent transition was found to be primarily associated with Mg segregation-induced grain boundary (GB) expansion and charge density depletion at the GB. These findings not only address the growing demand for durable lightweight materials for low-temperature applications, but also provide insights into the design of ultralight aerospace structural materials capable of withstanding the harsh environments encountered in space exploration.
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。
telier effect in an Al-Mg-Zn-based crossover aluminum alloyZhang, X.*; Li, Y.*; Wei, S.*; Guo, H.*; He, Z.*; Yang, C.*; Gong, W.; Harjo, S.; Zhou, D.*; Li, Z.*; et al.
Acta Materialia, 308, p.121990_1 - 121990_18, 2026/04
被引用回数：7 パーセンタイル：98.38(Materials Science, Multidisciplinary)Dynamic strain aging (DSA) causes serrated flow, known as the Portevin-Le Chtelier (PLC) effect, through interactions between solute atoms and dislocations. In this study, tensile tests on an Al-Mg-Zn crossover solid-solution alloy revealed that DSA and strain-induced dynamic precipitation jointly control serration behavior. At low strain rates, DSA-assisted precipitation produced Type C serrations, whereas high strain rates suppressed precipitation and promoted Type A serrations. High-energy X-ray diffraction and TEM analyses showed that screw dislocations dominated early deformation and governed plastic flow localization through cross-slip. Frequent cross-slip at high strain rates generated dislocation microbands responsible for Type A serrations, highlighting the primary role of screw dislocations rather than edge dislocations. A constitutive model incorporating DSA-assisted strengthening successfully predicted flow behavior over a wide strain-rate range.
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.
Ha, H.*; Kim, J.*; Gu, G. H.*; Harjo, S.; Gong, W.; Hong, S.-J.*; Kim, H. S.*
Materials Characterization, 234, p.116086_1 - 116086_12, 2026/04
被引用回数：2 パーセンタイル：84.58(Materials Science, Multidisciplinary)Dual-phase (DP) high- and medium-entropy alloys (H/MEAs), consisting of face-centered cubic (FCC) and body-centered cubic (BCC) phases, have attracted attention because of their excellent strength-ductility balance. However, the temperature dependence of hetero-deformation-induced (HDI) strengthening remains unclear. In this study, an Al
(CoNiV)
DP MEA was investigated using in-situ neutron diffraction and multiscale electron microscopy. Both intrinsic strength and HDI strengthening increased at cryogenic temperature. This enhancement originated from the increased lattice friction stress of the hard BCC phase and suppressed dislocation mobility at low temperature, which promoted dislocation accumulation at heterogeneous interfaces. These findings provide insights into temperature-dependent HDI strengthening in DP H/MEAs and related alloy systems.
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.
Ahn, S. Y.*; Kim, E. S.*; Jeong, S. G.*; Harjo, S.; 川崎 卓郎; Gong, W.; Kim, H.-J.*; Hong, S.-J.*; Hong, S. I.*; Kwon, H.*; et al.
Materials Science & Engineering A, 955, p.149839_1 - 149839_18, 2026/03
被引用回数：2 パーセンタイル：93.63(Nanoscience & Nanotechnology)Additive manufacturing (AM) of particle-reinforced metal matrix composites (MMCs) enables control of both strength and deformation behavior. In this study, TiC (2 wt%) nanoparticles were added to Fe
Co
NiCr
medium-entropy alloy (MEA) using directed energy deposition (DED). Although part of the TiC decomposed during processing, the released C and Ti stabilized the -austenite phase and suppressed deformation-induced martensitic transformation (DIMT), shifting deformation toward slip-dominated behavior. Microstructural observations revealed dispersed TiC particles and modified grain boundary morphology that promoted distributed plastic flow. In-situ neutron diffraction during tensile testing confirmed enhanced early-stage dislocation activity. These findings demonstrate that nanoparticle-induced phase stability changes strongly influence deformation mechanisms in AM-processed MMCs.
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.
Li, H.*; Gong, W.; 川崎 卓郎; Harjo, S.; Zheng, R.*; 他6名*
Acta Materialia, 305, p.121884_1 - 121884_10, 2026/02
被引用回数：3 パーセンタイル：96.93(Materials Science, Multidisciplinary)The quest for lightweight and highly formable magnesium (Mg) alloys has drawn significant attention due to the growing demand for energy-efficient structural materials. Achieving high ductility in Mg at room temperature, which is critical for mass production of structural components, remains a formidable challenge despite decades of research. In this study, we demonstrate super-ductility in an ultrafine-grained (UFG) Mg alloy at room temperature. By microalloying with trace manganese (Mn) and reducing the grain size to sub-micron scale, Mg-0.3Mn binary alloy achieves an exceptional room temperature tensile elongation of 135% at a quasi-static strain rate. Detailed microstructural analysis reveals that grain boundary (GB) sliding, rather than intragranular dislocation slip, is the dominant deformation mechanism in the UFG Mg-0.3Mn alloy. Unlike conventional alloying strategies that lead to GB pinning, the segregation of Mn element along GBs in a manner of nano-clusters could reduce interfacial bonding strength, acting as a lubricant to facilitate GB sliding and thus dramatically boost the ductility. This innovative GB engineering approach unlocks unprecedentedly remarkable deformability of Mg-based alloys at room temperature, paving the way for next-generation lightweight structural applications.
Gu, G. H.*; Jeong, S. G.*; Lee, J. H.*; Harjo, S.; Gong, W.; Amanov, A.*; Bae, J. W.*; Kwon, H.*; Kim, H. S.*
International Journal of Plasticity, 197, p.104581_1 - 104581_21, 2026/02
被引用回数：6 パーセンタイル：80.21(Engineering, Mechanical)Stacking fault energy (SFE) controls key deformation mechanisms in metals. This study demonstrates that apparent SFE and deformation behavior can be tuned by modifying only the near-surface microstructure (
100 um) through surface severe plastic deformation. The resulting gradient microstructure reduces apparent SFE, promoting martensitic transformation via preferential nucleation and stress partitioning. Consequently, mechanical properties are enhanced, achieving higher strength with minimal ductility loss, highlighting the effectiveness of localized microstructural engineering.
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
被引用回数：0 パーセンタイル：0.00(Chemistry, Physical)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：10 パーセンタイル：82.42(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：60.79(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.
Cantini, F.*; Ryan, J.*; Guidorzi, L.*; Magalini, M.*; Sans-Planell, O.*; Giudice, A. L.*; Garagiola, C.*; Re, A.*; Diana, E.*; 篠原 武尚*; et al.
Archaeological and Anthropological Sciences, 18(1), p.9_1 - 9_18, 2026/01
被引用回数：1 パーセンタイル：69.04(Anthropology)Iron artifacts from Japan's Kofun period (mid-3rd to early 7th century AD) are often recovered as heavily mineralized fragments, making it difficult to identify their original morphology and composition. Since archaeometallurgical studies require statistical analysis of many artifacts, non-destructive methods are essential. In this study, neutron tomography was applied to heavily mineralized iron sword fragments from Kofun-period tombs in Okayama Prefecture, Japan. The technique successfully visualized contrasts between iron-rich corrosion products and surrounding non-metal regions, enabling morphological analysis even when little metallic iron remained. Combined with neutron diffraction and X-ray techniques, the method provided new archaeometallurgical insights in a completely non-invasive manner.
Su, Y. H.; 篠原 武尚; Parker, J. D.*; 及川 健一; 甲斐 哲也; Gong, W.; 伊東 達矢; Harjo, S.; 相澤 一也; 鬼柳 善明*; et al.
Materials Science & Engineering A, 951, p.149607_1 - 149607_16, 2026/01
被引用回数：0 パーセンタイル：0.00(Nanoscience & Nanotechnology)Local variations in residual stress/strain and microstructure during fatigue crack growth in compact tension specimens of SUS304 austenitic stainless steel were investigated using complementary methods: pulsed neutron Bragg-edge imaging (NBEI), neutron diffraction (ND), digital image correlation (DIC) and electron backscatter diffraction (EBSD). Surface strain fields were evaluated using DIC and EBSD. NBEI provided two-dimensional averaged microstructure information, whereas ND yielded detailed three-dimensional distributions of residual lattice (elastic) strain and stress. This study particularly focused on how NBEI is helpful in understanding overall damage characteristics in the vicinity of a crack tip two-dimensionally. Distribution of microstructural parameters associated with crack growth, such as lattice constant, crystallite size, and texture, across the entire specimen was considered using Bragg-edge spectral analysis. The plastic zone in front of the crack tip, characterized by reduced crystallite size, was observed during crack propagation. After final fracture, two distinct zones with reduced crystallite size were identified: one caused by localized plastic deformation near the crack tip, and the other by bending at the back end of the specimen. This paper introduces the four experimental techniques and describes their respective features. Each method has its own advantages and limitations; However, by integrating their results, a more comprehensive understanding of the overall stress/strain field can be achieved.
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
被引用回数：10 パーセンタイル：92.28(Engineering, Mechanical)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.
neutron diffraction studyGong, W.; Harjo, S.; 川崎 卓郎; 山下 享介*; 柴田 曉伸*; 篠崎 智也*; 友田 陽*; 辻 伸泰*
Microstructures (Internet), 5(4), p.2025087_1 - 2025087_18, 2025/12
In-situ neutron diffraction during the thermomechanical controlled processing was employed to investigate the effect of ausforming on isothermal transformation below the martensite start temperature (Ms) in the NiCrMoV steel. After the occurrence of athermal martensitic transformation during cooling of the austenitized sample, the isothermal transformation below the Ms proceeded in two distinct stages: Stage 1, characterized by a rapid transformation rate, and Stage 2, which progressed more slowly. Ausforming suppressed both the athermal martensitic transformation and isothermal transformation in Stage 1 through mechanical stabilization. In contrast, ausforming accelerated the isothermal transformation in Stage 2, likely due to the enhanced carbon diffusion, indicating bainitic transformation characteristics in this stage. The resulting microstructure consisting of tempered martensite, bainite and retained austenite exhibited an excellent strength-ductility balance, achieving an ultimate tensile strength of 1989 MPa, a uniform elongation of 7.1%, and a total elongation of 16%. The present study provides new insights into phase transformation mechanisms below Ms and demonstrates the potential of ausforming-assisted processing for enhancing the mechanical properties of high-strength steels.
