Refractory high-entropy alloys fabricated using laser technologies: a concrete review

Refractory high-entropy alloys (RHEAs) have attracted widespread attention in recent years as multi-component alloys applied to high-temperature fields. High melting point elements endow special microstructures and properties to RHEAs, which differ from those of conventional alloys and pose a challenge to conventional fabricating technologies. Laser fabrication technologies are attractive in fabricating RHEAs since a high-power density laser beam can be used as a controllable heat source to quickly melt refractory elements and then followed by rapid cooling and solidification to optimize the dependent properties. This paper reviews recent research progress in the fabricating process and the influence of processing on microstructural evolution and phase formation of laser-fabricated RHEAs, aiming to address the use of laser technologies for improving room temperature and high-temperature properties of RHEAs, thereby providing a reference for research community. The current methods of laser fabricating RHEAs, namely selective laser melting, laser metal deposition and laser cladding, are first introduced, and then the relationships between chemical composition, microstructure and properties of RHEAs are analyzed from experimental and simulation perspectives. In addition, the microhardness, oxidation resistance, wear resistance, corrosion resistance, irradiation resistance, and biocompatibility of laser fabricated RHEAs are discussed. Finally, the critical challenges and opportunities for laser fabricating RHEAs in the research field are highlighted, based on the research perspective of this topic.