Phase stability and transformation in a light-weight high-entropy alloy

Light-weight high-entropy alloys (HEAs) with a vast alloy-design space have offered new avenues to explore novel low-cost, high strength-to-weight ratio structural materials. Studying their phase stability and possible transformations is critical for designing microstructures for optimal material properties. However, the complex local atomic environment of HEAs poses challenges to the fundamental understanding of phase stability and transformation behaviors. The present study investigates the phase stability and transformation behaviors of a newly-designed light-weight Al1.5CrFeMnTi HEA by integrated experimental and theoretical approaches. The coherent precipitation of the L2(1) phase within the body-centered-cubic (BCC) matrix at intermediate temperatures was observed, and the size, shape, coherency, and spatial distribution of the L2(1) phase were subsequently altered through selected annealing treatments. Moreover, the CALculation of PHAse Diagrams (CALPHAD) and first-principle calculations successfully optimize the compositions of light-weight HEAs with a coherent BCC/L2(1) two-phase structure. Shed light by the present study, novel light-weight HEAs, featuring the lower density (below 6 g/cm(3)) and cost, can be designed for high-temperature applications. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.