Eutectic high-entropy alloys and their applications in materials processing engineering: A review

Eutectic high-entropy alloys (EHEAs), combining the advantages of both eutectic alloys and high-entropy alloys (HEAs), possess good castability and superior comprehensive mechanical properties which are regarded as a revolutionary material system. In this paper, a current study of EHEAs is captured comprehensively for the first time, including basic theory, microstructure and deformation behavior, and alloy design. An in-depth analysis of the formation of different microstructures of EHEAs and their mechanical properties is presented, and four methods of designing EHEAs are summarized. Due to their unique characteristics, EHEAs show great potential in materials processing engineering. Here we give a comprehensive summary of their applications in welding, surface engineering, and additive manufacturing for the first time. Among them, EHEAs in welding are divided into three sections based on different welding techniques: fusion-based welding, solid-state welding, and diffusion reaction-based welding; EHEAs in surface engineering are separated into two parts: surface modification of bulk EHEAs and EHEA coatings; EHEAs in additive manufacturing are elaborated in two parts: laser powder bed fusion (LPBF) and laser direct energy deposition (LDED). Finally, a summary is given and a future outlook is prospected.