Influence of compositional complexity on species diffusion behavior in high-entropy solid-solution alloys

Detailed comparative molecular dynamics simulations of the diffusion process in a model quinary equiatomic FeNiCrCoCu FCC alloy are presented. Vacancy-assisted diffusion is studied by a statistical technique obtaining distributions of vacancy formation and migration energy values. In addition, vacancy migration is simulated using molecular dynamics at high temperatures and monitoring mean square displacements over time. To assess the role of compositional complexity, the results are compared to corresponding simulations in each of the pure individual components of the alloy as well as the corresponding "average atom" potential, with similar properties to the alloy but no compositional randomness. The comparison shows that the diffusion kinetics in the random alloy is not slower than in the average atom material or the average of the components, indicating that compositional fluctuations do not always result in "sluggish" diffusion. The results are compared with experimental data for self-diffusion in similar high-entropy alloys.