Role of chemical disorder and local ordering on defect evolution in high-entropy alloys

Abstract

High-entropy alloys (HEAs) have stimulated great interest due to their remarkable mechanical and irradiation performance. Experiments suggest that delayed defect evolution in HEAs, compared to conventional metals and dilute alloys, is the main reason for their improved irradiation resistance. However, the mechanism responsible for the observation remains elusive. Here we show that the potential energy landscape of defects under the influence of random arrangement of different species is the reason for the delayed defect evolution. We arrive at the conclusion by investigating the diffusion of defects and defect clusters under three cases: the averaged-atom model, random model, and the model with local short-range ordering. Our results suggest that, compared to the average model, the chemical fluctuation inherent in HEAs can suppress interstitial motion more than vacancy motion. The effects are more pronounced when SRO develops. For defect clusters, the chemical disorder can reduce their jump frequencies significantly and enhance correlation effects, leading to suppressed defect motion. Notably, we find that with SRO, such defect motion can be entirely trapped in local regions. This work demonstrates that chemical fluctuations and SRO are the main reason responsible for the suppressed defect evolution in HEAs, which dictates a promising way to improve the irradiation performance of HEAs through manipulating its chemical disorder states, such as local ordering.