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 highentropy 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 kdis was proposed to describe the disorder degree of MCIMs. As kdis 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 kdis 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.(c) 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The study investigates a partially disordered MCIM, C14 Laves phase, in a dual-phase CrHfNbTaTi refractory HEA, and determines its chemical formula and site preferences based on the observation of spatial atomic arrangement. It is found that the formation enthalpy of the C14 Laves phase in MCIM significantly increases due to local substitutions, resulting in higher energy and lower stability. Therefore, by manipulating the local substitution degree of the potential MCIM, the high-entropy solid solution can surpass MCIM even at intermediate temperatures. This study provides insights into the high-entropy effect and offers a valuable phase-regulation strategy for future HEA design.