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Journal Articles

Quantitative estimation method of the effect of segregated solute on hydrogen-enhanced decohesion at a grain boundary

Yamaguchi, Masatake; Ebihara, Kenichi; Itakura, Mitsuhiro; Tsuru, Tomohito

Scripta Materialia, 255, p.116366_1 - 116366_5, 2025/01

 Times Cited Count:0

Reduction of grain boundary cohesive energy by hydrogen has been considered as one of the candidate causes of grain boundary fracture in steels and aluminum alloys. Recently, the effects of grain boundary segregation elements have been investigated by first-principles calculations, but there are few studies that quantitatively estimate the grain boundary cohesive energy. In this study, we describe a quantitative evaluation method using first-principles calculation results and show some examples of experimental calculations.

Journal Articles

New insight on the thermal impact on cementitious materials due to high-temperature with water supply; Continuous expansive spalling in water

Miura, Taito*; Miyamoto, Shintoro*; Maruyama, Ippei*; Aili, A.*; Sato, Takumi; Nagae, Yuji; Igarashi, Go*

Case Studies in Construction Materials, 21, p.e03571_1 - e03571_14, 2024/12

 Times Cited Count:0 Percentile:0.00(Construction & Building Technology)

Journal Articles

Effect of carbon segregation at prior austenite grain boundary on hydrogen-related crack propagation behavior in 3Mn-0.2C martensitic steels

Okada, Kazuho*; Shibata, Akinobu*; Kimura, Yuji*; Yamaguchi, Masatake; Ebihara, Kenichi; Tsuji, Nobuhiro*

Acta Materialia, 280, p.120288_1 - 120288_14, 2024/11

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

Journal Articles

Systematic experimental and model-based evaluation of the synergistic effects of alloy composition and damage rate on the formation of Cr-rich precipitates in Fe-Cr-Al alloys under ion irradiation

Abe, Yosuke; Sasaki, Taisuke*; Yamashita, Shinichiro; Okubo, Nariaki; Ukai, Shigeharu

Journal of Nuclear Materials, 600, p.155271_1 - 155271_12, 2024/11

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

To investigate the formation behavior of Cr-rich precipitates (CrRP) in Fe-Cr-Al (ODS) alloys being developed as accident tolerant fuel cladding for light water reactors, 14 Fe-Cr-Al alloys with systematically varied Cr and Al compositions were irradiated with 10.5 MeV Fe$$^{3+}$$ at $$350^{circ}$$C at three damage levels. A three-dimensional atom probe analysis showed that the CrRP number density, volume fraction, and Cr concentration increase with increasing Cr composition, decreasing Al composition, and decreasing dose rate. The result of the multiple regression analysis on CrRP volume fractions indicates that in addition to the primary effects of these variables, there are several important interactions. It was also highlighted that to understand the dose rate effect on the CrRP formation behavior under neutron irradiation, it is useful to examine the irradiation time dependence, including the effective use of thermal aging data as a limit to the zero dose rate.

Journal Articles

Martensitic transformation-governed Luders deformation enables large ductility and late-stage strain hardening in ultrafine-grained austenitic stainless steel at low temperatures

Mao, W.*; Gao, S.*; Gong, W.; Kawasaki, Takuro; Ito, Tatsuya; Harjo, S.; Tsuji, Nobuhiro*

Acta Materialia, 278, p.120233_1 - 120233_13, 2024/10

 Times Cited Count:1 Percentile:71.29(Materials Science, Multidisciplinary)

Journal Articles

Uranium-plutonium-oxygen phase diagram; Investigating the solvus of fluorite's exsolution

Vauchy, R.; Hirooka, Shun; Horii, Yuta; Ogasawara, Masahiro*; Sunaoshi, Takeo*; Yamada, Tadahisa*; Tamura, Tetsuya*; Murakami, Tatsutoshi

Journal of Nuclear Materials, 599, p.155233_1 - 155233_11, 2024/10

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

The fluorite exsolution/recombination in U$$_{1-y}$$Pu$$_{y}$$O$$_{2-x}$$ (y = 0.30 and 0.45) and PuO$$_{2-x}$$ was investigated using differential scanning calorimetry. The results are in relatively good agreement with the literature data, except for plutonia. Our values indicate that the critical temperature of the miscibility gap in Pu-O is 30$$sim$$50 K lower than previously reported. Finally, the systematic experimental procedure allowed us refining the locus of the solvus existing in hypostoichiometric U$$_{0.70}$$0Pu$$_{0.30}$$O$$_{2-x}$$, U$$_{0.55}$$Pu$$_{0.45}$$O$$_{2-x}$$, and PuO$$_{2-x}$$ dioxides.

Journal Articles

Oxide particles in oxide dispersion strengthened steel neutron-irradiated up to 158 dpa at Joyo

Toyama, Takeshi*; Tanno, Takashi; Yano, Yasuhide; Inoue, Koji*; Nagai, Yasuyoshi*; Otsuka, Satoshi; Miyazawa, Takeshi; Mitsuhara, Masatoshi*; Nakashima, Hideharu*; Onuma, Masato*; et al.

Journal of Nuclear Materials, 599, p.155252_1 - 155252_14, 2024/10

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

We investigated the stability of oxide nano particles in oxide dispersion-strengthened (ODS) steel, which is a promising candidate material for next-generation reactors, under neutron irradiation at high temperature to high doses. MA957, a 14Cr-ODS steel, was irradiated with Joyo in Japan Atomic Energy Agency under irradiation conditions of 130 dpa at 502$$^{circ}$$C, 154 dpa at 589$$^{circ}$$C, and 158 dpa at 709$$^{circ}$$C. Three-dimensional atom probe (3D-AP) and transmission electron microscope (TEM) observation were performed to characterize the oxide particles in the ODS steels. A high number density of Y-Ti-O particle was observed in the unirradiated and irradiated samples. Almost no change in the morphology of the oxide particles, i.e. average diameter, number density, and chemical composition, has been observed in the samples irradiated to 130 dpa at 502$$^{circ}$$C and to 154 dpa at 589$$^{circ}$$C. A slight decrease in number density was observed in the sample irradiated to 158 dpa at 709$$^{circ}$$CC. The hardness of any of the irradiated samples was almost unchanged from that of the unirradiated sample. It was revealed that the oxide particles existed stable, and the strength of the material was sufficiently maintained even after being neutron irradiated to high dose of $$sim$$160 dpa at high temperature up to 700$$^{circ}$$C. A part of this study includes the results of MEXT Innovative Nuclear Research and Development Program Grant Number JPMXD0219214482.

Journal Articles

Oxygen potential measurement of U$$_{0.85}$$Am$$_{0.15}$$O$$_{2}$$ at 1473, 1573, and 1673 K

Watanabe, Masashi; Yokoyama, Keisuke; Vauchy, R.; Kato, Masato; Sugata, Hiromasa*; Seki, Takayuki*; Hino, Tetsushi*

Journal of Nuclear Materials, 599, p.155232_1 - 155232_5, 2024/10

 Times Cited Count:2 Percentile:82.00(Materials Science, Multidisciplinary)

Oxygen potential data of U$$_{0.85}$$Am$$_{0.15}$$O$$_{2-x}$$ were measured at 1473, 1573, and 1673 K by thermogravimetry. In U$$_{1-y}$$An$$_{y}$$O$$_{2-x}$$, where An stands for Pu or Am, and for a given value of y and Oxygen/Metal ratio, the oxygen potential of U$$_{1-y}$$Am$$_{y}$$O$$_{2-x}$$ is higher than that of U$$_{1-y}$$Pu$$_{y}$$O$$_{2-x}$$. The valence of cations in the hypostoichiometric region is similar to that of Nd-doped UO$$_{2}$$. At the stoichiometric composition, it is estimated to be Am$$^{3+}$$, U$$^{4+}$$, and U$$^{5+}$$ (for charge compensation of Am$$^{3+}$$). The experimental data were analyzed using a defect chemistry model, and a relationship connecting the oxygen-to-metal ratio, the temperature, and the equilibrium oxygen partial pressure was proposed.

Journal Articles

Temperature dependence of deformation and fracture in a beta titanium alloy of Ti-22V-4Al

Yano, Rei*; Tanaka, Masaki*; Yamasaki, Shigeto*; Morikawa, Tatsuya*; Tsuru, Tomohito

Materials Transactions, 65(10), p.1260 - 1267, 2024/10

Impact tests and tensile tests were conducted between 77K and 450K in order to elucidate the temperature dependence of absorbed-impact energy, yield stress, effective shear stress, activation volume, and activation enthalpy. The impact-absorbed energy decreased with decreasing test temperature, however, this alloy did not undergo low-temperature embrittlement although it has a bcc structure. Tensile tests showed changes in both the work-hardening rate and the temperature dependence of yield stress at approximately 120 K. This suggests a change in the mechanism behind the plastic deformation at the temperature. The temperature dependence of the activation enthalpy for dislocation glide suggests that double-kink nucleation of a screw dislocation is the dominant mechanism for the dislocation glide from 150K to 200 K, while the interaction between a dislocation and solute atoms dominantly controls the dislocation glide above 200 K. Superelasticity appears in stress-strain curves tested below 120 K, suggesting that the yielding is governed by transformation-induced plasticity below 120 K. The enhanced toughness at low temperatures in these alloys is discussed from the viewpoint of dislocation shielding theory.

Journal Articles

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

Zhang, Y.-J.*; Umeda, Takemasa*; Morooka, Satoshi; Harjo, S.; Miyamoto, Goro*; Furuhara, Tadashi*

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

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

Journal Articles

Enhancing mechanical properties of medium Mn steel by warm rolling based on laminated elemental segregation

Chen, H. F.*; Liu, B. X.*; Xu, P. G.; Fang, W.*; Tong, H. C.*; Yin, F. X.*

Journal of Materials Research and Technology, 32, p.3060 - 3069, 2024/09

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

Journal Articles

Enthalpy measurement on (U$$_{1-x}$$Pu$$_{x}$$)O$$_{2}$$ (x = 0, 0.18, 0.45, and 1) and analysis of heat capacity

Hirooka, Shun; Morimoto, Kyoichi; Matsumoto, Taku; Ogasawara, Masahiro*; Kato, Masato; Murakami, Tatsutoshi

Journal of Nuclear Materials, 598, p.155188_1 - 155188_9, 2024/09

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Origin of excellent strength-ductility balance unique to FCC high-entropy alloys; A Plaston-based mechanism derived from electronic structure calculations

Tsuru, Tomohito

Materials Transactions, 65(9), p.988 - 994, 2024/09

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

Some high-entropy alloys (HEAs) with the face-centered cubic (FCC) structure have an excellent strength-ductility balance. While unique deformation modes such as fine twinning patterns other than dislocation glide contribute to the mechanical properties, it has not understood what fundamental properties and features of HEAs cause such unique deformation. In the present study, fundamental properties responsible for the excellent mechanical properties of CoCrFeNiMn and its subsystems were explored comprehensively by the first-principles calculations. The local lattice distortion reaches almost 2% of the Burger vector, which contributes to improving strength in HEAs. Furthermore, the stacking fault energy (SFE) was significantly low in random solid solution, while it increases around some domains where the short-range order (SRO) is formed. The increase in the SFE is caused by the disturbance of the chemical SRO and the spin order due to the SF formation. Our calculations suggest that low and high SFE domains distributed in a solid solution region unique to HEAs lead to successive activation of various deformation modes (Plaston), which achieves excellent strength-ductility balance.

Journal Articles

Dramatic elastic response at the critical end point in UTe$$_2$$

Vali$v{s}$ka, M.*; Haidamak, T.*; Cabala, A.*; Posp$'i$$v{s}$il, J.*; Bastien, G.*; Sechovsk$'y$, V.*; Prokle$v{s}$ka, J.*; Yanagisawa, Tatsuya*; Opletal, P.; Sakai, Hironori; et al.

Physical Review Materials (Internet), 8(9), p.094415_1 - 094415_9, 2024/09

 Times Cited Count:0

Journal Articles

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

 Times Cited Count:1 Percentile:71.29(Nanoscience & Nanotechnology)

Journal Articles

Ferroaxial transitions in glaserite-type Na$$_2$$Ba${it M}$(PO$$_4$$)$$_2$$ (${it M}$ = Mg, Mn, Co, and Ni)

Kajita, Yoichi*; Nagai, Takayuki*; Yamagishi, Shigetada*; Kimura, Kenta*; Hagihara, Masato; Kimura, Tsuyoshi*

Chemistry of Materials, 36(15), p.7451 - 7458, 2024/08

 Times Cited Count:0 Percentile:0.00(Chemistry, Physical)

Journal Articles

In-situ X-ray imaging of the breakup dynamics of current-carrying molten metal jets during arc discharge

Sato, Yuriko*; Shobu, Takahisa; Tominaga, Aki; Sano, Tomokazu*; Ogino, Yosuke*

Communications Materials (Internet), 5, p.147_1 - 147_9, 2024/08

The flow dynamics of current-carrying molten metal jet breakup during arc discharge serves as mass and heat sources in wire-arc-based metal deposition processes, thereby optimizing the resultant product quality. However, the spatiotemporal flow interaction between the molten metal jet and the surrounding arc plasma remains unclear. Here, using in-situ synchrotron X-ray imaging, we simultaneously track surface deformation and internal flow in molten aluminum jets during argon arc discharge. We reveal that modulating the magnitude and path of the arc discharge current can accelerate the jet velocity by 200 $$sim$$ 300% beyond its initial injection speed, thereby facilitating significant jet elongation. Our results provide consistent evidence that the jet flow dynamics are predominantly governed by the interaction between the arc discharge current and its coaxial self-induced magnetic field. This study establishes a framework at the intersection of fluid dynamics and electromagnetism, contributing to optimized control and precision in wire-arc-based applications.

Journal Articles

Interaction of CsOH with structural steel 316L and simulated products of the steel-cladding reaction under assumed conditions relevant for the accident at the Fukushima Dai-Ichi Unit 2 and 3

Pshenichnikov, A.; Zubekhina, B.

Journal of Nuclear Materials, 597, p.155136_1 - 155136_12, 2024/08

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

Journal Articles

Anisotropic creep property related to non-spherical shape of mechanically alloyed powder of oxide dispersion strengthened F82H

Sakasegawa, Hideo; Nakajima, Motoki*; Kato, Taichiro*; Nozawa, Takashi*; Ando, Masami*

Materials Today Communications (Internet), 40, p.109659_1 - 109659_8, 2024/08

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

Nanometric oxide particles play an important role in improving the creep property of Oxide Dispersion Strengthened (ODS) steels. In our previous research, we examined a microstructural feature known as prior particle boundary (PPB). PPB refers to the surface of mechanically alloyed (MA) powders before consolidation. We revealed that the ODS steel with fine PPBs produced from smaller MA powders, exhibited shorter creep rupture times, compared to that with coarse PPBs produced from larger MA powders. The size of MA powders had an impact on the creep property. In this study, we examined the shape of MA powders, which were non-spherical shapes. Such shapes have the potential to induce anisotropic creep behavior. We conducted small punch creep tests on specimens with two different orientations to study the possible anisotropy. The results revealed that the creep rupture times varied depending on the orientation of specimen, thus indicating anisotropic creep property.

Journal Articles

Multi-modal 3D image-based simulation of hydrogen embrittlement crack initiation in Al-Zn-Mg alloy

Higa, Ryota*; Fujihara, Hiro*; Toda, Hiroyuki*; Kobayashi, Masakazu*; Ebihara, Kenichi; Takeuchi, Akihisa*

Materials Transactions, 65(8), p.899 - 906, 2024/08

 Times Cited Count:0 Percentile:0.00(Materials Science, Multidisciplinary)

It is indispensable to suppress hydrogen embrittlement (HE) to develop the strength of the Al-Zn-Mg alloy. Because intergranular fracture (IGF) is mainly observed when HE occurs in the alloy, we need to understand the IGF initiation to suppress HE. In the present study, we investigated the stress, strain, and H concentration, which influence the IGF initiation, in actual fractured regions by simulation of a crystal plasticity finite element method and H diffusion analysis in a 3D image-based model, which was created based on 3D polycrystalline microstructure data obtained from X-ray imaging technique. Combining the simulation and in-situ observation of the tensile test sample by X-ray CT, we examined the stress, strain, and H concentration, and discussed the IG crack initiation condition. As a result, it is revealed that stress normal to grain boundary induced by crystal plasticity dominates IG crack initiation while the accumulation of H due to stress has little impact on it.

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