Experimental Validation of the Calphad Approach Applied to Multi-Principle Element Alloys

High entropy alloys (HEAs) are a recent area of research in materials science. Their namesake is because their high entropy of mixing due to multiple metallic elements in a near equimolar ratio. The high entropy of mixing is supposed to suppress unwanted, brittle, ordered intermetallic phases, and form a single, randomly mixed solid solution phase. This phenomena makes HEAs a good candidate for structural applications. However, this entropy of mixing may not be enough to suppress all intermetallic phases. For this reason, the CALculation of PHAse Diagrams (CALPHAD) approach is being explored to predict phase equilibrium in HEAs. This study seeks to experimentally validate the current CALPHAD approach when applied to HEAs. Five alloy compositions were characterized with SEM, EDS, and XRD in the as-cast condition and after equilibrium heat treatments of 500hr at 1000°C and 1000hr at 750°C. Phases detected in the experimental alloys were compared with the CALPHAD predicted equilibrium phases. When considerations are taken, the current CALPHAD approach is adequate in predicting phase equilibrium for HEAs