A comprehensive review on the deformation behavior of refractory high entropy alloys at elevated temperatures

Thermo-mechanical processing of refractory high entropy alloys (RHEAs) at high temperatures is very important. It is an effective method of modifying the microstructure, properties, and shaping into final components after casting. Using the Scopus database, 57 articles relating to the hot deformation of refractory high entropy alloys were extracted from 2011 to 2022. Despite the limited number of articles on hot deformation of RHEAs, it is important to find out if the dominant softening mechanisms reported in other metallic alloys are evident. This is the main impetus for this study since the hot deformation behavior has not been comprehensively studied. All the probable mechanisms influencing deformation in metallic alloys, such as work hardening, dynamic recrystallization, and dynamic recovery, have also been observed in RHEAs. The bulging phenomenon, serrated grain boundaries, and necklace-like structures reported in metallic alloys have also been detected in hot deformed RHEAs. Unsafe deformation behavior such as cracks that have been reported in metallic alloys, have also been observed in RHEAs. This review has provided a comprehensive study on the hot working processes of RHEAs and highlighted critical gaps for future research direction with some suggested limitations.