Effect of irradiation on randomness of element distribution in CoCrFeMnNi equiatomic high-entropy alloy

The stability of the structure and composition of the alloy is important in structural materials. Therefore, in this study, the distribution of each element in the CoCrFeMnNi equiatomic high-entropy alloy (HEA), which is considered to have a random distribution, was examined experimentally and theoretically. Furthermore, the effect of ion irradiation at different temperatures on the distribution of each element was investigated. The experimental results based on the positron annihilation spectroscopy showed that there was not significant element segregation in the well-annealed CoCrFeMnNi HEA. Moreover, the distribution of the elements in CoCrFeMnNi HEA was approximately the same despite the alloy being irradiated to 0.5 dpa (displacement per atom) at the damage peak at temperatures of 300, 573, and 773 K. In addition, the randomness of the element distribution in the equilibrium structure of the CoCrFeMnNi HEA was investigated using the first-principles simulation. The calculation results showed that despite the favorable affinity between Ni and Cr in the CoCrFeMnNi HEA, the constituent elements in the alloy were disordered. In addition, the same-type atomic pairings of an element with itself, especially Cr-Cr, were all depleted.