Controlling microstructure and mechanical properties of Ti-V-Cr-Nb-Ta refractory high entropy alloys through heat treatments

In this study, we have investigated the microstructure and mechanical properties of two refractory high entropy alloys (RHEAs), Ti-V-Cr5-Nb-Ta and Ti-V-Cr-Nb-Ta, in their as-cast and heat-treated conditions. Both alloys show almost single-phase BCC structure, while different size and volume fraction of secondary phases were formed after homogenisation heat treatment. The major secondary phase was indexed as a complex C15 Laves structure with a composition of (Ti, Ta)(V, Cr, Nb)2. The nanoindentation mapping indicates C15 Laves phase is very hard and brittle, performing a homogenisation heat treatment leads to an improved hardness in both alloys. The correlations between hardness changes and microstructural evolutions after homogenisation heat treatment are also discussed.(c) 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).