A critical review on solid-state welding of high entropy alloys– processing, microstructural characteristics and mechanical properties of joints

Abstract

The high entropy alloys (HEAs) are the newly developed high-performance materials that have gained significant importance in defence, nuclear and aerospace sector due to their superior mechanical properties, heat resistance, high temperature strength and corrosion resistance. These alloys are manufactured by the equal mixing or larger proportions of five or more alloying elements. HEAs exhibit superior mechanical performance compared to traditional engineering alloys because of the extensive alloying composition and higher entropy of mixing. Solid state welding (SSW) techniques such as friction stir welding (FSW), rotary friction welding (RFW), diffusion bonding (DB) and explosive welding (EW) have been efficiently deployed for improving the microstructural integrity and mechanical properties of welded HEA joints. The HEA interlayers revealed greater potential in supressing the formation of deleterious intermetallic phases and maximizing the mechanical properties of HEAs joints. The similar and dissimilar joining of HEAs has been manifested to be viable for HEA systems which further expands their industrial applications. Thus, the main objective of this review paper is to present a critical review of current state of research, challenges and opportunities and main directions in SSW of HEAs mainly CoCrFeNiMn and AlxCoCrFeNi alloys. The state of the art of problems, progress and future outlook in SSW of HEAs are critically reviewed by considering the formation of phases, microstructural evolution and mechanical properties of HEAs joints.