Effects of Al addition on Vickers hardness increase by thermal aging of Fe-Cr-Al alloys; Evaluation by systematic experiments, machine learning modeling, and first-principles calculations

Abe, Yosuke; Tsuru, Tomohito; Fujita, Yohei*; Otomo, Masahide*; Sasaki, Taisuke*; Yamashita, Shinichiro; Okubo, Nariaki; Ukai, Shigeharu

Journal of Nuclear Materials, 606, p.155606_1 - 155606_12, 2025/02

https://doi.org/10.1016/j.jnucmat.2025.155606

We investigated the effect of Al addition on the formation of phase in Fe-Cr-Al model alloys by thermal aging. The Vickers hardness tests and a machine learning model indicate that the formation of the phase is promoted by low Al additions and suppressed by high Al additions. First-principles calculations, which indicate that Cr-Al-vacancy pairs are more stable than Cr-Cr pairs and that including Al atoms during phase nucleation may be energetically advantageous. On the other hand, the formation of Al-Al pairs was very unstable. The formation of Al-Al pairs near the interface can be avoided when the amount of Al addition is small. However, it is inevitable when the amount of Al addition is significant, leading to the instability of the phase.

Fabrication of (Bi)(BiTe) superlattice films by Te desorption from a pristine BiTe film

Kusaka, Shotaro*; Sasaki, Taisuke*; Sumida, Kazuki; Ichinokura, Satoru*; Ideta, Shinichiro*; Tanaka, Kiyohisa*; Hono, Kazuhiro*; Hirahara, Toru*

Applied Physics Letters, 120(17), p.173102_1 - 173102_5, 2022/04

https://doi.org/10.1063/5.0090207

Progress in R&D efforts on the energy recovery linac in Japan

Sakanaka, Shogo*; Ago, Tomonori*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; Harada, Kentaro*; Hiramatsu, Shigenori*; Honda, Toru*; et al.

Proceedings of 11th European Particle Accelerator Conference (EPAC '08) (CD-ROM), p.205 - 207, 2008/06

Future synchrotron light sources based on the energy-recovery linacs (ERLs) are expected to be capable of producing super-brilliant and/or ultra-short pulses of synchrotron radiation. Our Japanese collaboration team is making efforts for realizing an ERL-based hard X-ray source. We report recent progress in our R&D efforts.

Effect 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*; Tsuru, Tomohito; Fujita, Yohei*; Otomo, Masahide*; Yamashita, Shinichiro; Okubo, Nariaki; Ukai, Shigeharu

no journal, , 

This study examines CrRP formation behavior through 10.5 MeV self-ion irradiation at 350C on 14 Fe-Cr-Al alloy compositions, with doses of 0.24 and 0.64 dpa and three damage rates differing by two orders of magnitude. Using a three-dimensional atom probe, we analyzed CrRPs in irradiated samples and evaluated the effects of different variables with a correlation matrix and multiple regression model. We found that the number density, volume fraction, and internal Cr concentration of CrRPs increased with higher Cr levels, lower Al levels, and reduced damage rates. To better understand the atomic-level mechanisms, we also explored the effect of Al addition on CrRP formation using first-principles calculations, analyzing atomic arrangement energy and short-range order parameters alongside experimental data.

Formation behavior of Cr-rich phase in Fe-Cr-Al alloys under ion irradiation

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

no journal, , 

In Fe-Cr-Al alloys, which are being developed as accident-resistant fuel cladding for light water reactors, it is a challenge to accurately predict the precipitation behavior of the Cr-rich embrittlement phase ( phase), which occurs at relatively low temperature irradiations. However, the formation behavior of the phase under neutron irradiation is not well understood due to global limitations of irradiation reactors. In this study, the influencing factors (Cr concentration, Al concentration, and damage rate) on phase formation were quantitatively evaluated by combining systematic irradiation experiments for 14 types of alloys at three levels of damage rate and multiple regression analysis. The results also contributed to the development of more accurate /(+) phase boundary curves based on Cr and Al concentrations, which are important in actual alloy design.

Effect 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*; Tsuru, Tomohito; Yamashita, Shinichiro; Okubo, Nariaki; Ukai, Shigeharu

no journal, , 

In oxide dispersion strengthened Fe-Cr-Al alloys being developed for the accident tolerant fuel cladding of the light water reactors, it is challenging to elucidate and predict the embrittlement behavior due to Cr-rich precipitates (CrRPs). We have systematically investigated the formation behavior of CrRPs in 14 Fe-Cr-Al alloys irradiated with 10.5 MeV self-ions at three different dose rates using a three-dimensional atom probe. The effect of each experimental variable on the CrRP-related quantities was evaluated using a correlation matrix and multiple regression model. The results showed that CrRP number density, volume fraction, and Cr concentration in CrRPs increased with increasing Cr composition, decreasing Al composition, and decreasing dose rate. First-principles calculations were performed to investigate the effect of Al addition on the formation behavior of CrRPs at the atomic level, and the results were discussed by comparison with experiments.