Composition of Intermetallic Phases in High-Entropy Alloys: Compositional Inheritance of High-Entropy Sigma Phases from Binary Counterparts

Despite many merits, the design of high-entropy alloys (HEAs) containing intermetallic (IM) phases remains a daunting challenge due to insufficient fundamental knowledge regarding higher-order IMs. Here, the chemical compositions of a model IM, the sigma phase, were collected and analyzed in 60 HEAs to reveal their constitutions, concentration ratios, and VEC. It was found that σ phases in HEAs were primarily composed of binary-sigma-forming-pair (BSFP) elements and can be regarded as higher-order solid solutions of binary σ phases. The elemental ratios and valence electron concentrations within the σ phases were both directly influenced by the BSFPs within the HEAs. These results show that besides structure, the constitution, concentration ratio, and other physical characteristics of IM phases in HEAs can also be inherited from their corresponding binary counterparts. Such inheritances imply a wider possibility to optimize the compositions, characteristics, and perhaps also the properties of IM phases in multi-component systems through the selection of BSFPs.