Effects of minor alloying addition on He bubble formation in the irradiated FeCoNiCr-based high-entropy alloys

Minor alloying with specific elements is an effective approach to tailor material's properties, but it has not been introduced to modify the radiation effects of high-entropy alloys (HEAs), which are a promising material for nuclear application. In the work, a 0.2 molar ratio of Al/Cu/Ti was respectively added into the quaternary FeCoNiCr HEA, they were then irradiated by 2 MeV He ions at four temperatures from 673 to 973 K. After irradiation, He bubble behavior in specimens were investigated by the transmission electron microscopy (TEM). The results showed that bubbles in the minor alloying HEAs usually had a larger size, lower number density, and broader distribution range, comparing to their parent alloy. Such effects were more significant at a higher irradiation temperature and most pronounced by the Ti-addition. Atomistic simulations revealed that such minor alloying addition could relatively reduce the energy barrier for vacancy migration and formation in FeCoNiCr system, which thereby promotes He diffusion through the replacement or vacancy mechanism. The theoretical models for He bubble formations verified our results that a higher He diffusivity in the minor alloying HEAs can enhance bubble growth and lower its nucleation numbers during irradiation. The phase stability of irradiated HEAs were also examined and its potential influences on bubble evolution were pointed out. This study provides insights on tailoring radiation defects via the conventional alloying strategy.