Insights into the phase diagram of the CrMnFeCoNi high entropy alloy using electromagnetic melting and casting

Abstract

International audienceHigh entropy alloys are single phase metallic materials, composed of more than 4 elements in equi-atomic proportionwhich is the maximum in the configurational entropy. In order to study the thermodynamics of those alloys, anequimolar CrMnFeCoNi HEA was processed by electromagnetic melting, casting and annealing under varyingconditions (cooling rate and annealing duration) and the evolution of the structure and microstructure was studied. Aftercasting, a dendritic microstructure was formed whose characteristic length depends on the cooling rate. Annealing leadsto a chemical homogenization of the microstructure. Indeed a true solid-solution down to the atomic scale wasevidenced in an HEA by atom probe tomography. It was shown that this face-centered cubic single-phase solid solutionis the high temperature stable state of the equimolar CrMnFeCoNi alloy. By analogy with completely miscible binaryalloy, the CrMnFeCoNi HEA can be described by a schematic phase diagram of the CrFeCo - MnNi system consistingof a liquidus and a solidus