Refractory high entropy alloys (RHEAs) show considerable potential as ultra-high temperature materials due to their very high melting point (> 2000 °C) and unique property of strength retention at elevated temperature. In the present study, CrMoNbTiW RHEA is synthesized through mechanical alloying followed by spark plasma sintering (MA+SPS) and casting route. Besides a major BCC solid solution, few secondary phases were observed in the powder metallurgy route compared to a single-phase BCC solid solution in the casting route. Further, constant strain rate (10-3 – 10-1 s-1) compression tests were done at 1000 – 1350 °C on sintered and cast samples using GLEEBLE 3800. The ultra-fine grain size in MA+SPS alloy led to 50% elongation. Continuous dynamic recrystallization and flow localization were identified as the softening mechanism. Further, TEM studies revealed dislocation glide as the deformation mechanism at 1300 °C – 10-1 s-1 MA+SPS RHEA.
As-cast RHEA demonstrated higher strength than MA-WM+SPS RHEA at the cost of ductility. Among various strengthening mechanisms, solid solution strengthening was the dominant mechanism contributing to such a high strength. A simple solid solution strengthening model based on the lattice distortion has been used to predict the yield strength of cast RHEA. The materials constants such as shear modulus, Burgers vector, and Poisson’s ratio significantly affect the variation of yield stress with increasing temperature.