Single-phase high-entropy alloys - an overview

Abstract

The term “high-entropy alloys (HEAs)” first appeared about 10 years ago defining alloys composed of n=5–13 principal elements with concentrations of approximately 100/n at.% each. Since then many equiatomic (or near equiatomic) single- and multi-phase multicomponent alloys were developed, which are reported for a combination of tunable properties: high hardness, strength and ductility, oxidation and wear resistance, magnetism, etc. In our paper, we focus on probably single-phase HEAs (solid solutions) out of all HEAs studied so far, discuss ways of their prediction, mechanical properties. In contrast to classical multielement/multiphase alloys, only single-phase multielement alloys (solid solutions) represent the basic concept underlying HEAs as mixing-entropy stabilized homogenous materials. The literature overview is complemented by own studies demonstrating that the alloys CrFeCoNi, CrFeCoNiAl0.3 and PdFeCoNi homogenized at 1300 and 1100°C, respectively, for 1 week are not single-phase HEAs, but a coherent mixture of two solid solutions.