Examining the thermodynamic stability of mixed principal element oxides in AlCoCrFeNi high-entropy alloy by first-principles

Abstract

Understanding the complex oxidation behavior of alloys consisting of multiple principal elements is critical to realize their potential for high temperature structural applications. We examine the thermodynamic stability of primary and mixed oxides for one such extensively examined high-entropy alloy (HEA), AlCoCrFeNi, using first-principles calculations. Our predictions indicate that Cr2O3 and Al2O3 are the most stable oxides both at the ground state and elevated temperatures, with the relative ordering for oxide stability at higher temperatures being similar to that at 0 K. The presence of both Al with Cr are most likely to form protective oxide layers, while that produced by Ni and Cr are the least stable. Nevertheless, the gradient of formation energies for the stable mixed Cr2O3-type oxides with increasing concentration of other principal elements becomes steeper with increasing temperature.