Stability of High Entropy Alloys to Spinodal Decomposition

Abstract

When a high entropy alloy (HEA) system contains a single binary miscibility gap, the gap spreads across the entire composition space of the system. Beneath the miscibility gap is a spinodal hypersurface above which HEAs are stable to a continuous change of phase via spinodal decomposition. When there are additional binary miscibility gaps, the stability limits appear separately at high temperature but combine on cooling to form a continuous surface that may contain a cone point, an important feature for the design of age hardening alloys. In this work, an understanding of how spinodal surfaces form, combine, and develop critical features is obtained by investigating several ternary systems each with three binary miscibility gaps. Because their topology is the same, bisection isopleths and isothermal sections of ternary phase diagrams given in this work will help interpret calculated bisection isopleths and isotherms of 5- and 6-dimensional HEA phase diagrams.