Abstract

High entropy alloys have proved to exhibit excellent irradiation resistance due to their high interstitial-vacancy recombination rate and modified defect dynamics. In this work, molecular dynamics (MD) simulations were used to study the evolution of irradiation-induced defects of CoCrFeNi and Al0.3CoCrFeNi under the successive bombardments at different temperatures, with the goal of revealing the influence of Al element. The accumulation of defects, the evolution of clusters and dislocations, and the element distributions of surviving defects for the two alloys were compared. It was founded that the inclusion of Al increased the accumulation rate of point defects in the initial stage of accumulated damage, but had no discernible effect on the number of point defects in the regime where overlapping recoil happened. In spite of this, Al0.3CoCrFeNi exhibited a better irradiation resistance than CoCrFeNi, evidenced by the less desirable formation of large-sized interstitial clusters, large-sized vacancy clusters, and SFTs in Al0.3CoCrFeNi. This might be due to the reduced interstitial mobility and the facilitated nucleation of vacancy cluster, resulting from the oversized Al atoms. The addition of Al and the elevated temperature suppressed the formation of large 1/3<111> Frank loops, i.e., promoted the transformation from 1/3<111> Frank loops to 1/2<110> perfect loops. Three ways of the formation of large Frank loops and two ways of the transformation from Frank loops to perfect loops were revealed. The quantity of surviving Cr, Ni, Co, and Fe elements inside the two HEAs was arranged in a decreasing order, which might have an impact on the radiation-induced segregation of HEAs.

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