High temperature deformation behavior and microstructural evolution of an ultrafine-grained and multiphase CrMoNbTiW refractory high entropy alloy

The present study investigates the deformation behavior of an equiatomic CrMoNbTiW refractory high entropy alloy (RHEA) synthesized via powder metallurgy. The alloy displayed a dominant BCC phase with secondary TiC and Cr₂Nb phases. Uniaxial compression tests were performed at temperatures ranging from 1000 to 1350 °C and strain rates of 10⁻¹ to 10⁻³ s⁻¹. The flow stress data were analyzed using an Arrhenius-type power law, revealing a strong dependence of the apparent activation energy and stress exponent on temperature, strain, and strain rate. The ultrafine-grained microstructure and secondary phases facilitated continuous dynamic recrystallization (CDRX). However, flow localization was observed under all deformation conditions. Nanoindentation analysis indicated distinct deformation behaviors among the different phases, with the W-rich BCC phase exhibiting higher deformation resistance compared to TiC. These findings highlight the importance of analyzing the post-deformation microstructure of multiphase materials to elucidate the underlying deformation mechanisms.