Computational design of non-equiatomic CoCrFeNi alloys towards optimized mechanical and surface properties

Multi-principal element alloys (MPEAs), also known as high-entropy alloys, are often designed to be equiatomic from entropy considerations. We show that relaxing such constraint could lead to enhanced mechanical and surface properties, which is critical for applications of MPEAs under complex environment where both stress and corrosion attacks occur. Specifically, using spin-polarized density functional theory calculations, the effects of chromium (Cr) concentration on the mechanical and surface properties of CoCrFeNi with similar to 16, 25, and 34 at.% Cr were studied. It was found that Cr plays significant roles in affecting both mechanical properties and surface reactivity. Alloys with higher Cr percentage showed higher Young's modulus and Poisson's ratio, as well as higher chemical activity of surface Cr atoms. Overall, a non-equiatomic composition of Co22Cr34Fe22Ni22 was predicted with simultaneously optimized strength and surface reactivity.