Abnormal γ″ - ε phase transformation in the CoCrFeNiNb0.25 high entropy alloy

Abstract Thermodynamically, the multi-principal-component compositions of high entropy alloys (HEAs) bring diversified phase transformation paths. In this study, we report that a γ″ phase precipitates from the face centered cubic (FCC) matrix and then abnormally transforms into a e phase, instead of the δ phase as reported in superalloys. The e phase has a (NiCo) 3 Nb-type hexagonal crystal structure. The phase transformation takes places in a manner of peritectoid reaction: γ″ + FCC → e. The present findings indicate a high probability for researchers to find new efficient strengthening phases as well as interesting phase transformation mechanism in HEAs.