Explosive Welding and Friction Stir Welding/Processing of Multi-Principal Element Alloys.

Medium- and high-entropy alloys (MEAs/HEAs) or multi-principal element alloys are a new class of promising alloys with wide application possibilities in several industries like nuclear, offshore, liquefied natural gas, and transportation, among others. The development of these revolutionary alloys comes with the need to separately unravel their weldability as the microstructure and the welding-induced thermal responses of the single, dual, and multi-phase HEAs differ. Detailed knowledge of the weldability of MEAs/HEAs is still at the early stage and remains a useful link between the developed MEAs/HEAs and their full-scale industrial manufacturing applications. The intense heat input of fusion welding techniques easily introduces different or combined challenges such as elemental segregation, inhomogeneous phase transformation, solidification cracking, and coarsened structure to the weld metals of HEAs. As a result, this paper provides a state-of-the-art review of the low heat-input or solid-state welding and friction stir processing of MEAs/HEAs. The welding section covers explosive and friction stir welding processes of HEAs. Insights into the future research areas that can further progress the scientific understanding and weldability of MEAs/HEAs are briefly explicated in this paper. [ABSTRACT FROM AUTHOR]