Element-dependent evolution of chemical short-range ordering tendency of NiCoFeCrMn under irradiation

The evolution of short-range order (SRO) structures under irradiation has a great impact on the mechanical properties of high-entropy alloys. In this study, the atomistic mechanism of the evolution of SRO during and after cascade collisions was investigated in NiCoFeCrMn by multiscale modeling using molecular dynamics and lattice kinetic Monte Carlo simulations. SRO structures could be destructed by cascade collisions in short time and recovered by atomic diffusion in a much longer time. The destruction rate depends on the primary knock-on atom energies in cascade collisions and shows a universal law with respect to the number of replacement-per-atom. The vacancy diffusion simulations reveal that the SRO recovery rates of different element pairs vary significantly due to the distinct diffusion rates. Consequently, the SRO state under irradiation differs from that in thermodynamic equilibrium due to the difference of destruction and recovery rate for each element pair. The evolution of SRO is a result of the competition between the destruction and recovery mechanisms and depends heavily on the irradiation conditions.