Atomistic simulations of enhanced irradiation resistance and defect properties in body-centered cubic W-V-Cr and W-Ta-V alloys

Abstract

Compared to face-centered cubic (fcc) high-entropy alloys (HEAs), body-centered cubic (bcc) medium/high-entropy alloys (M/HEAs) generally possess larger lattice distortion and exhibit distinct defect properties. In this work, molecular dynamics (MD) simulations of collision cascades and molecular statics (MS) calculations of defect properties were performed to investigate the irradiation resistance mechanism revealed from the point defect behaviors in W-V-Cr and W-Ta-V alloys. Low vacancy formation and migration energies with large energy spreads suggest the higher vacancy concentration and fast diffusions near the thermal spike. Slow self-interstitial atom (SIA) diffusions and fast vacancy diffusions lead to the closer mobilities of vacancies and SIAs, which significantly promotes the encountering probability and enhances the defect recombination in the cooling process of the thermal spike. Furthermore, formation and binding energies of W- and Ta-containing dumbbells are significantly larger than that of V- and Cr-related dumbbells, leading to higher occurrence probabilities and surviving fractions of V and Cr SIAs. Weak binding abilities of V and Cr SIAs can effectively suppress the clustering behaviors and make the surviving SIA clusters smaller. Our findings suggest that the irradiation resistance mechanisms in bcc M/HEAs are different from that in fcc M/HEAs, providing a deeper understanding of the radiation resistance mechanism in bcc M/HEAs with large lattice distortion.