Refractory high-entropy alloys: A review of preparation methods and properties

Alloying is one of the main ways to achieve desirable properties in materials. The design concept is based on one or two metal elements, supplemented with multiple trace elements to achieve altered or optimized properties. With the advancement in technology, the traditional alloy has evolved from simple to complex compositions, thus improving their properties and promoting the progress of civilization. High-entropy alloys (HEAs) are a new type of multi-master alloys that are popular in the recent two decades. Unlike conventional alloys, HEAs comprise multiple alloying elements according to the isoatomic or non-isoatomic ratios and have several unique properties, such as high strength and hardness, excellent wear and corrosion resistance, thermal stability, and irradiation resistance. Refractory high-entropy alloys (RHEAs), HEAs made of refractory metals, have attracted great attention because of their excellent high-temperature mechanical properties. This paper discusses RHEAs from three aspects: processing methods, microstructure, and properties. Finally, this work presents the development and future prospects of RHEAs. RHEAs represented by MoNbTaVW alloys show better compressive yield strengths at high temperatures and a slower change of yield strength with temperature than traditional Ni-based high-temperature alloys. Compared with commercial superalloys, refractory metals, refractory alloys, and tool steels, RHEAs, such as MoNbTaVW, MoNbTaTiZr, and HfNbTiZr, show excellent wear resistance. RHEAs represented by W₃₈Ta₃₆Cr₁₅V₁₁ have no dislocation ring defect structure and excellent anti-irradiation performance after irradiation, except for the precipitation of small particles in the second phase. In this paper, two directions of future development of RHEAs were proposed: (1) establishing high-throughput experimental and computational methods to continue exploring composition and structural models of RHEAs and (2) exploring the service behavior of RHEAs in a multi-field coupled environment.