Competition between solid solution and multi-component Laves phase in a dual-phase refractory high-entropy alloy CrHfNbTaTi

Solid solution phases dominate the thermodynamic competition with intermetallic phases in high-entropy alloys (HEAs), known as the high-entropy effect. However, owing to inevitable local substitutions in multi-component intermetallics (MCIMs), imposed thermodynamic changes are often overlooked. This study investigated a partially disordered MCIM, C14 Laves phase, in a dual-phase CrHfNbTaTi refractory HEA. The chemical formula and site preferences were determined based on the observation of spatial atomic arrangement. Furthermore, a parameter k_dis was proposed to describe the disorder degree of MCIMs. As k_dis increased from 0 to 0.2 due to local substitutions, the formation enthalpy of the C14 Laves phase significantly increased, resulting in higher energy and lower stability. Therefore, when feasible composition regulation and site occupancy design are adopted to manipulate the k_dis of the potential MCIM, the high-entropy solid solution is able to be superior to the MCIM even at intermediate temperatures. The study provides insights into the high-entropy effect by considering MCIM enthalpies, providing a valuable phase-regulation strategy for future design of HEAs.