Enhancing the mechanical properties of high-entropy alloys through severe plastic deformation: A review

Abstract

High-entropy alloys (HEAs) are one of the breakthroughs in the past decade in alloy development that have the potential to exhibit outstanding physical, mechanical, and chemical properties. This allows HEAs to be highly versatile materials for use in a variety of applications. Through reasonable composition design and post-manufacturing processes, HEAs can show superior properties compared to traditional alloys, which are highly demanded for novel emerging technologies. Severe plastic deformation (SPD) has been known as one of the most popular post-manufacturing processes for enhancing the mechanical properties of HEAs. However, there is still a lack of knowledge about the microstructure, physical, and mechanical properties of HEAs subjected to SPD processes. This review is concerned with the production of nano/ultrafine-grained HEAs using SPD techniques such as severe cold rolling (SCR), high-pressure torsion (HPT), and equal channel angular pressing (ECAP). Also, the characteristics of HEAs with respect to SPD are demonstrated, such as reduced grain growth and phase decomposition. These characteristics increase the possibility of producing nanostructured high-entropy alloys (NsHEAs) with multiple principal elements by SPD processes or by post-annealing and enable extremely high superplasticity at high strain rates. Finally, these findings introduce SPD as not only a processing tool to improve the physical and mechanical properties of HEAs, but also as a synthesis tool to fabricate novel HEAs with superior properties compared to conventional engineering materials, especially for high-tech applications.