Numerical verification for the effect of suppressing hydrogen embrittlement by Sn doping in the Al-Zn-Mg alloy

Ebihara, Kenichi; Fujihara, Hiro*; Shimizu, Kazuyuki*; Yamaguchi, Masatake; Toda, Hiroyuki*

International Journal of Hydrogen Energy, 136, p.751 - 756, 2025/06

https://doi.org/10.1016/j.ijhydene.2024.05.146

It has been experimentally reported that adding tin (Sn) to high-strength aluminum-zinc-magnesium (Al-Zn-Mg) alloys effectively suppresses hydrogen (H) embrittlement, which may be attributed to H absorption by the second-phase particles of Sn. To verify this fact, a simulation of H entry into the Sn phase in Al was performed using a model based on the reaction-diffusion equation that incorporates the solid solution energy of H evaluated by first-principles calculations. The results showed that the H solid solution site concentration of the second-phase particles must be at least five times higher than that of the Al phase for H absorption by the Sn second-phase particles to suppress H embrittlement. Therefore, the actual H embrittlement suppression effect of Sn second-phase particles is limited, and other factors may influence the suppression of H embrittlement in the experiment.

Measurement and analysis of long-term variation of atmospheric Be activity concentrations in Dazaifu (western Japan)

Narazaki, Yukinori*; Sakoda, Akihiro; Akata, Naofumi*; Ito, Hisanori*; Momoshima, Noriyuki*

Journal of Environmental Radioactivity, 284, p.107612_1 - 107612_7, 2025/04

https://doi.org/10.1016/j.jenvrad.2024.107612

Atmospheric Be activity concentration was continuously measured in Dazaifu, western Japan, from 1999 to 2020, and its variation was analyzed. Daily Be data analysis, encompassing an analysis for 22 years, revealed a concentration range of not detected - 18 mBq/m, characterized by substantial monthly variation and smoothed annual variation. An average daily Be activity concentration of 5.0 2.6 mBq/m was considered to be representative at the ground-surface-level in 30-40N. Results from a two-way Analysis of variance (ANOVA) indicated statistical significance in monthly and annual Be variabilities. The monthly variability of Be activity concentration was approximately four times greater than the annual variability. Frequency analysis revealed that the monthly variability comprised major 12-month and minor 6-month periodicities. The substantial decrease in Be activity concentration during summer, a primary driver of monthly variation, was also observed at other locations in Japan, attributed to a stable high-pressure system in the Pacific Ocean that stalled over Japan's southern seas, followed by the inflow of air masses containing low Be activity concentrations. The annual variation was primarily influenced by the 11-year solar activity cycle, which affects the intensity of cosmic rays that produce Be.

Evaluation of analytical uncertainty in quantitative determination of elements; The Case of boron

Sumita, Takehiro*; Osawa, Takahito; Chiu, I.-H.; Ikeda, Atsushi

Analytica Chimica Acta, 1329, p.343256_1 - 343256_10, 2024/11

https://doi.org/10.1016/j.aca.2024.343256

Study on heat transfer behavior of a cylindrical particle bed with volumetric heating

Wen, J.*; Kamada, Yuto*; Yokoyama, Kosei*; Matsumoto, Tatsuya*; Liu, W.*; Morita, Koji*; Imaizumi, Yuya; Tagami, Hirotaka; Matsuba, Kenichi; Kamiyama, Kenji

Proceedings of 13th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS13) (Internet), 8 Pages, 2024/11

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

https://doi.org/10.1016/j.jnucmat.2024.155252

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 502C, 154 dpa at 589C, and 158 dpa at 709C. 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 502C and to 154 dpa at 589C. A slight decrease in number density was observed in the sample irradiated to 158 dpa at 709CC. 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 160 dpa at high temperature up to 700C. A part of this study includes the results of MEXT Innovative Nuclear Research and Development Program Grant Number JPMXD0219214482.

Chiral gauge field in fully spin-polarized magnetic Weyl semimetal with magnetic domain walls

Ozawa, Akihiro*; Araki, Yasufumi; Nomura, Kentaro*

Journal of the Physical Society of Japan, 93(9), p.094704_1 - 094704_9, 2024/09

https://doi.org/10.7566/JPSJ.93.094704

Modulation of magnetization in magnetic Weyl semimetals leads to the shift of Weyl points in momentum space, which effectively serves as the chirality-dependent gauge field for the Weyl fermions. Here, we theoretically study such a magnetization-induced chiral gauge field, in a fully spin-polarized Weyl ferromagnet CoSnS. From a tight-binding model of CoSnS on stacked kagome lattice with magnetism, we calculate the magnetization-dependent evolution of the Weyl points in momentum space, resulting in the chiral gauge field. In the presence of the magnetic domain wall structure, we evaluate the chiral magnetic field arising from the spatial profile of the chiral gauge field. We find that a magnetic domain wall in CoSnS gives rise to a giant chiral magnetic field for the Weyl fermions, which reaches the order of a few hundred tesla to induce the Landau quantization. Such a giant chiral magnetic field may also influence the novel transport phenomena, such as the charge pumping by the domain wall motion, compatible with the spinmotive force.

Variation analysis of atmospheric Be activity concentrations with respect to precipitation

Narazaki, Yukinori*; Sakoda, Akihiro; Akata, Naofumi*; Ito, Hisanori*; Momoshima, Noriyuki*

Journal of Environmental Radioactivity, 277, p.107432_1 - 107432_7, 2024/07

https://doi.org/10.1016/j.jenvrad.2024.107432

Beryllium-7 activity concentrations in the atmosphere and precipitation were continuously measured every day between April 2011 and December 2015 in Dazaifu, western Japan. The measured data were quantitatively analyzed to determine the precipitation-induced variation in Be activity concentrations. The average concentrations on nonprecipitation and precipitation days were 5.5 and 3.8 mBq/m, respectively. This difference of 31% (1.7 mBq/m) on average, was attributable to the washout effect, which was more significant in the summer. Regarding the association between Be activity concentration and precipitation, the concentration remained at a similar level for the small precipitation amount of 5.0 mm/day and showed a decreasing trend (but was insignificant) for the precipitation of 5.0-10.0 mm/day. A significant decrease in the concentration was observed for 10 mm/day. Furthermore, when precipitation occurred on two successive days, the Be activity concentrations on the second day significantly decreased regardless of precipitation.

Assessment of hydrogen embrittlement behavior in Al-Zn-Mg alloy through multi-modal 3D image-based simulation

Fujihara, Hiro*; Toda, Hiroyuki*; Ebihara, Kenichi; Kobayashi, Masakazu*; Mayama, Tsuyoshi*; Hirayama, Kyosuke*; Shimizu, Kazuyuki*; Takeuchi, Akihisa*; Uesugi, Masayuki*

International Journal of Plasticity, 174, p.103897_1 - 103897_22, 2024/03

https://doi.org/10.1016/j.ijplas.2024.103897

Hydrogen(H) embrittlement in high-strength aluminum(Al) alloys is a crucial problem. H accumulation at the interface of precipitates in Al alloy is considered to cause embrittlement. However, there is no quantitative knowledge regarding the interaction between H distribution and stress field near cracks. In this study, using a multi-modal three-dimensional image-based simulation combining the crystal plasticity finite element method and H diffusion analysis, we tried to capture the stress distribution near the crack, its influence on the H distribution, and the probability of crack initiation in the experimental condition. As a result, it was found that grain boundary cracks transition to quasi-cleavage cracks in the region where the cohesive energy of the semi-coherent interface of MgZn precipitates decreases due to H accumulation near the tip. We believe the present simulation method successfully bridges nanoscale delamination and macroscale brittle fracture.

Double-differential cross sections for charged particle emissions from particle impinging on Al at 230 MeV/u

Furuta, Toshimasa*; Uozumi, Yusuke*; Yamaguchi, Yuji; Iwamoto, Yosuke; Koba, Yusuke*; Velicheva, E.*; Kalinnikov, V.*; Tsamalaidze, Z.*; Evtoukhovitch, P.*

Journal of Nuclear Science and Technology, 61(2), p.230 - 236, 2024/02

https://doi.org/10.1080/00223131.2023.2294192

Charged particle production from particle fragmentation reactions was investigated experimentally by measurement of 230-MeV/u particles bombarding an aluminum target. Double differential cross sections were measured for each ejectile of p, d, t, He, and He at laboratory angles between 15 and 60 deg. The results of analyzed data found the following common characteristics: (1) spectra of proton- and neutron-emission are similar in high energy region at forward angle, (2) triton-to-He ratio of -breakup yield is 1:2, which is similar to lower incident energy experiment, and (3) the shape of broad peak formed by He and particles could be explained by the process with collision between induced particle and target nucleus.

Stress corrosion cracking induced by the combination of external and internal hydrogen in Al-Zn-Mg-Cu alloy

Tang, J.*; Wang, Y.*; Fujihara, Hiro*; Shimizu, Kazuyuki*; Hirayama, Kyosuke*; Ebihara, Kenichi; Takeuchi, Akihisa*; Uesugi, Masayuki*; Toda, Hiroyuki*

Scripta Materialia, 239, p.115804_1 - 115804_5, 2024/01

https://doi.org/10.1016/j.scriptamat.2023.115804

Stress corrosion cracking (SCC) behaviors induced by the combination of external and internal hydrogen (H) in an Al-Zn-Mg-Cu alloy were systematically investigated via in situ 3D characterization techniques. SCC of the Al-Zn-Mg-Cu alloy could initiate and propagate in the potential crack region where the H concentration exceeded a critical value, in which the nanoscopic H-induced decohesion of -MgZn precipitates resulted in macroscopic cracking. External H that penetrated the alloy from the environment played a crucial role during the SCC of the Al-Zn-Mg-Cu alloy by generating gradient-distributed H-affected zones near the crack tips, which made Al alloys in water environment more sensitive to SCC. Additionally, the pre-existing internal H was driven toward the crack tips during plastic deformation. It was involved in the SCC and made contributions to both the cracks initiation and propagation.