Effects of single and simultaneous Fe, He ions irradiations on CoCrFeMnNi high entropy alloy

Abstract

Simultaneous irradiation was performed on CoCrFeMnNi high entropy alloy (HEA) at room temperature using Fe ions and He ions, and single Fe ions irradiation and single He ions irradiation were used as comparisons. The synergistic effect of the two ions on irradiation-induced defects such as dislocation loops and He bubbles, as well as the effect of irradiation damage on the nano-hardness were investigated. As the irradiation dose increased, a distribution with small and dense dislocation loops was first formed in CoCrFeMnNi HEA, and then these dislocation loops merged and grew. However, compared to pure metal, CoCrFeMnNi HEA entered the dislocation loop merging stage at a higher threshold dose due to its higher defect recombination capacity and higher critical stress of initial dislocation motion. Compared with the single Fe ions irradiation, the addition of He in the simultaneous irradiation accelerated the merging and growth of dislocation loops and decreased the density of dislocation loops. At the same He dose, simultaneous irradiation produced a higher vacancy concentration than single He ions irradiation, which increased He mobility, leading to wider He bubble layer and larger He bubble size. CoCrFeMnNi HEA hardened after irradiation with all three parameters in the order of single He ions irradiation > single Fe ions irradiation > simultaneous Fe+He ions irradiation. This study provided a deeper understanding of the irradiation damage mechanism of HEA in complex irradiation environment.