Phase, microstructure and compressive properties of refractory high-entropy alloys CrHfNbTaTi and CrHfMoTaTi

New refractory high-entropy alloys, CrHfNbTaTi and CrHfMoTaTi, derived from the well-known HfNbTaTiZr alloy through principal element substitution were prepared using vacuum arc melting. The phase components, microstructures, and compressive properties of the alloys in the as-cast state were investigated. Results showed that both alloys were composed of BCC and cubic Laves phases. In terms of mechanical properties, the yield strength increased remarkably from 926 MPa for HfNbTaTiZr to 1258 MPa for CrHfNbTaTi, whereas a promising plastic strain of around 15.0% was retained in CrHfNbTaTi. The morphology and composition of the network-shaped interdendritic regions were closely related to the improved mechanical properties due to elemental substitution. Dendrites were surrounded by an incompact interdendritic shell after Mo incorporation, which deteriorated yield strength and accelerated brittleness.