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) as well as by casting route. Besides a major BCC solid solution, few secondary phases are observed in the powder metallurgy route in contrast to a single-phase BCC solid solution in the casting route. Further, constant strain rate (10-3 to 10-1 s-1) compression tests were done at 1000 1350 ℃ on sintered and cast samples. The ultra-fine grain size in MA+SPS alloy led to 50% elongation along with the observation of localized deformation zones. Moreover, dynamic recrystallization and 111> γ-fiber texture was observed in the MA+SPS RHEA. In the cast alloy, precipitation of the Laves phase along with BCC solid solution resulted in increased strength at expense of the percentage of elongation. An attempt is made to understand the deformation of as-cast alloy using a solid solution strengthening model. The predicted yield strength values as a function of temperature were found to be significantly affected by the temperature dependent material constants, resulting in a wide range of yield strength values. The absolute value of yield strength depends on the shear modulus, whereas the yield strength variation with temperature is affected by the Poissons ratio. A plausible deformation mechanism of the RHEA is explained based on the analysis of compressive mechanical data together with microstructural characterization studies.
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