Phase prediction, microstructure and high hardness of novel light-weight high entropy alloys

Guided by CALPHAD modeling, low-density and multiphase three novel High Entropy Alloys (HEAs), Al40Cu15Cr15Fe15Si15, Al65Cu5Cr5Si15Mn5Ti5 and Al60Cu10Fe10Cr5Mn5Ni5Mg5 were produced by large scale vacuum die casting. A mixture of simple and complex phases was observed in the as-cast microstructures, which demonstrates good agreement with CALPHAD results. The measured densities varied from 3.7 g/cm3 to 4.6 g/cm3 and microhardness from 743 Hv to 916 Hv. Finally, the hardness of all the light-weight HEAs (LWHEAs) with densities below 4.6 g/cm3 manufactured to date were reviewed. The hardness of Al40Cu15Cr15Fe15Si15 and hardness to density ratio of Al65Cu5Cr5Si15Mn5Ti5 are the highest of all LWHEAs reported up to date. Keywords: High entropy alloys, High hardness, Light-weight, Calphad, Microstructure, Phase composition, Complex Concentrated Alloys