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.

Strong flux pinning by columnar defects with directionally dependent morphologies in GdBCO-coated conductors irradiated with 80 MeV Xe ions

Sueyoshi, Tetsuro*; Kotaki, Tetsuya*; Furuki, Yuichi*; Fujiyoshi, Takanori*; Semboshi, Satoshi*; Ozaki, Toshinori*; Sakane, Hitoshi*; Kudo, Masaki*; Yasuda, Kazuhiro*; Ishikawa, Norito

Japanese Journal of Applied Physics, 59(2), p.023001_1 - 023001_7, 2020/02

https://doi.org/10.35848/1347-4065/ab6f2b

We show that Xe ion irradiation with 80 MeV to GdBaCuOy-coated conductors creates different morphologies of columnar defects (CDs) depending on the irradiation angles relative to the c-axis: continuous CDs with a larger diameter are formed for oblique irradiation at = 45, whereas the same ion beam at a different angle ( = 0) induces the formation of discontinuous CDs. The direction-dependent morphologies of CDs significantly affect the angular behavior of the critical current density .

Spontaneous formation of suboxidic coordination around Co in ferromagnetic rutile TiCoO film

Hu, W.*; Hayashi, Koichi*; Fukumura, Tomoteru*; Akagi, Kazuto*; Tsukada, Masaru*; Happo, Naohisa*; Hosokawa, Shinya*; Owada, Kenji; Takahashi, Masamitsu; Suzuki, Motohiro*; et al.

Applied Physics Letters, 106(22), p.222403_1 - 222403_5, 2015/06

https://doi.org/10.1063/1.4921847

Evaluation of fracture toughness of fine-grained isotropic graphites for HTGR

Yamada, Teruaki*; Matsushima, Yuki*; Kuroda, Masatoshi*; Sumita, Junya; Shibata, Taiju; Fujita, Ichiro*; Sawa, Kazuhiro

Nuclear Engineering and Design, 271, p.323 - 326, 2014/05

https://doi.org/10.1016/j.nucengdes.2013.11.055

In order to investigate the effects of the experimental methodology and the notch angle on the fracture toughness of the fine-grained isotropic nuclear graphites IG-110 and IG-430, the three-point-bending test, which has been recently proposed as the methodology to evaluate the fracture toughness of graphite for high temperature gas-cooled reactors (HTGRs), was performed using two types of the specimens with different notch angles. The results obtained in this study could be summarized as follows: (1) The values of the fracture toughness of IG-110 and IG-430 measured in this study were 0.890 MPa m and 1.031 MPa m, respectively. It was also found that the value of the fracture toughness of IG-110 was nearly equal to or smaller than the values obtained by the other method reported previously. (2) The values of the fracture toughness of the fine-grained isotropic graphites were not affected between the notch angles introduced by the incisive razor blade. (3) The ratio of the tensile strengths of IG-110 and IG-430 was estimated from Griffith Theory using the experimental data obtained in this study. The estimated strength ratio was in good agreement with the strength ratio obtained from the supplier's data.

Angular dependence of critical current density and -values in BaZrO/YBaCuO quasi-multilayered films with columnar defects

Sueyoshi, Tetsuro*; Kotaki, Tetsuya*; Fujiyoshi, Takanori*; Mitsugi, Fumiaki*; Ikegami, Tomoaki*; Ishikawa, Norito

Physica C, 494, p.153 - 157, 2013/11

https://doi.org/10.1016/j.physc.2013.04.073

BaZrO/YBaCuOy quasi-multilayered films, in which the size and the spatial distribution of BaZrO nano-particles were controlled, were irradiated using 200 MeV Xe ions along the c-axis direction. Whenthe BaZrO nano-particles were larger in size, the flux lines not captured by CDs, such as interstitial fluxlines between CDs and double kinks of flux lines, can be pinned more effectively by the BaZrO nano-particles, so that the Jc enhances for high magnetic fields and high temperature. In addition, the inverse correlation between Jc and n-value appears at high temperature in increasing magnetic field for the film with correlated rows of the nano-particles which might be curved off the c-axis. These suggest that the hybrid flux pinning depends not only on the combination of one-dimensional (1D) and three-dimensional pinning centers (3D-PCs) but also on the size and the spatial distribution of the 3D-PCs.

Separation in -phase of BiPb alloy under mega-gravity

Okayasu, Satoru; Ono, Masao; Nishio, Taichiro*; Iguchi, Yusuke*; Mashimo, Tsutomu*

Defect and Diffusion Forum, 323-325, p.545 - 548, 2012/04

https://doi.org/10.4028/www.scientific.net/DDF.323-325.545

Atomic sedimentation in solid occurs under mega-gravity treatment. As the result, partially melt-growth in -phase of BiPb-alloy occurs. Small difference of densities between fully hcp structure of BiPb and that of partially defected BiPb are enhanced under mega-gravity, and cause the separation of the -phase. Superconducting properties differs between the separated two phases.

Isotope distribution in pure indium after liquid-state centrifugation

Ono, Masao; Okayasu, Satoru; Esaka, Fumitaka; Haruki, Rie; Mashimo, Tsutomu*

Journal of the Japan Society of Microgravity Application, 28(2), p.S89 - S91, 2011/04

http://www.e-jasma.com/arc/paper/J1319435226

An ultracentrifuge experiment was performed on a pure liquid-indium at acceleration field of 8.210 g at 300C for 100 hours. The isotope ratio measurements were performed on the centrifuged specimen with Secondary Ion Mass Spectrometer (CAMECA IMS-6f). In/In isotope ratio on the specimen changed with negative gradient in the direction of centrifugal force approximately 1.3%. The measurement result indicated that the heavy In isotopes moved in the direction of the centrifugal force and the light In isotopes moved in the counter direction in the specimen. At the session, we will present both the result and an approach to find a precondition to develop an isotope separation process using the phenomenon.

Electrolytic reduction mechanism of Np(V) and the effect of coexisting nitric acid

Kitatsuji, Yoshihiro; Kimura, Takaumi; Kihara, Sorin*

IOP Conference Series; Materials Science and Engineering, 9, p.012078_1 - 012078_7, 2010/05

https://doi.org/10.1088/1757-899X/9/1/012078

The behaviors of reduction of Np(V) by controlled potential electrolysis were studied, and a unique time course of electrolysis current was observed. It was conclude that Np(V) was reduced by two reduction processes that are the chemical reaction with Np(III) and the electrocatalytic reduction by adsorbed hydrogen atom on platinum electrode surface. The time course of current for controlled potential electrolysis of Np(V) under various condition of the solution was investigated, and the effects of the concentration of H and NO on electrolysis behaviour were shown.

Isotope fractionation due to sedimentation of atoms in centrifuged indium-lead alloy

Ono, Masao; Iguchi, Yusuke*; Okayasu, Satoru; Esaka, Fumitaka; Kobayashi, Katsura*; Hao, T.; Bagum, R.*; Osawa, Takahito; Fujii, Kimio; Nakamura, Eizo*; et al.

Defect and Diffusion Forum, 289-292, p.63 - 68, 2009/04

The atomic-scale graded structure of In-Pb alloy was formed by an ultracentrifuge experiment under conditions that a gravitational field of 0.8110 G for 100 hours at 150 C in solid state in our previous study. The isotope ratio measurements were performed on the centrifuged sample with secondary ion mass spectrometer (SIMS). Pb/Pb and Pb/Pb isotope ratio changed with negative gradient in the direction of centrifugal force approximately 1.5% and 0.8%, respectively. And three-isotope diagram of Pb/Pb versus Pb/Pb proved that the isotope fluctuation depends on isotopic mass difference. These results showed that the strong gravitational field not only affected on the inter-diffusion but also on self-diffusion in this alloy as causing isotope fractionation effect, and the isotope fractionation was dependent on mass-difference.

Formation of amorphous graded structure in BiPb intermetallic compounds under strong gravitational field

Mashimo, Tsutomu; Iguchi, Yusuke*; Bagum, R.*; Sano, Tomokazu*; Takeda, Shingo*; Kimura, Shigeru*; Sakata, Osami*; Ono, Masao; Okayasu, Satoru; Tsurui, Takao*; et al.

Defect and Diffusion Forum, 289-292, p.357 - 360, 2009/04

A visible four-layers structure with anomalous nano-sturucture was formed from a homogeneous e-phase BiPb intermetallic compound under a strong gravitational field (1.0210 G, 130C, 100 hours). In the 4th layer (lowest-gravity region), pure Bi particles precipitate. In the 2nd 3rd layers, composition graded structures, where Pb content increased along the gravity direction, were formed. It was found that the very broad XRD peak appeared in the 2nd layer, which indicated that an amorphous structure was contained.