Refractory high entropy superalloys (RSAs)

Complex, concentrated alloys (CCAs) containing refractory principal elements and Al can have microstructures with disordered body-centered cubic (BCC) and ordered B2 phases that are remarkably similar to superalloys. The simple idea of copying superalloy microstructures in these BCC-based refractory alloys introduces a set of audacious challenges. BCC metals and B2 compounds are often brittle at room temperature; the B2 phase is unstable in refractory-Al binaries and reasons for its stability in higher-order systems are a mystery; and many refractory metals and alloys display catastrophic oxidation. Here we discuss opportunities and challenges to develop RSAs as new high temperature structural materials. Published by Elsevier Ltd on behalf of Acta Materialia Inc.