Exploring the inhibitory effect of WTaVCr high-entropy alloys on hydrogen retention: From dissolution, diffusion to desorption

Abstract

Due to the excellent resistance to radiation damage, high-entropy alloys (HEAs) have been considered as important candidates for nuclear materials. However, to realize the great potential of HEAs in fusion energy, it is important to consider the hydrogen (H) behaviors, which remain to be elucidated. Here, we systematically investigate the dissolution, diffusion and desorption of H in equiatomic WTaVCr using the first-principles calculations. It is found that the H solution energy in WTaVCr is lower than that in pure W, which can be clarified by the H affinity of metallic elements and the available volume of interstitial sites. Accordingly, a possible diffusion path of interstitial H is selected, containing 26 metastable sites, and the corresponding energy barrier is 0.46 eV. Besides, the maximum trapping energy and accommodation number of H at a mono-vacancy in WTaVCr is only 0.30 eV and 3 ∼ 5 H, respectively, which is much lower than that in pure W (1.28 eV and 12 H). More importantly, because of the low trapping energy and moderate diffusion energy barrier, the desorption temperature of H from a mono-vacancy is lower than the room temperature, implying that vacancies are not efficient trapping centers for interstitial H atoms in WTaVCr. Therefore, although the equilibrium interstitial H concentration in WTaVCr is higher than that in pure W, H retention at high temperatures and H-induced blistering are suppressed due to the weak H-defect interactions. Our results will provide a good reference for understanding the H behaviors in HEAs.