High-entropy alloys: An overview on the fundamentals, development, and future perspective

High-Entropy Alloys (HEAs) is a revolutionary concept of the alloy design field proposed in 2004. It provides a much greater scope of composition design than ever before. The four core effects of HEAs could lead to good combinations of properties and allow tuning the crystal structures and microstructures of the system. The fundamental physical metallurgy principles of HEAs are different from those of the conventional alloys in many aspects, and the deformation mechanisms of HEAs are particularly interesting to the community. Recently, a new mechanism of strengthening and toughening by high slip-plane density in HEAs has been proposed. Since HEAs possess great potentials for various applications, several types of HEAs have been developed, such as low stacking fault high-entropy alloys (LSF-HEAs), high-entropy superalloys (HESAs), refractory high-entropy alloys (RHEAs), high-entropy metallic glasses (HEMGs), eutectic high-entropy alloys (EHEAs), high-entropy intermetallic compounds (HEICs), and high-entropy Coatings (HE-Coatings). In this article, the basic concept and definition of HEAs are described. Furthermore, the four core effects are reviewed and clarified. The recent progresses of developing LSF-HEAs, HESA, HEMGs, RHEAs, EHEAs, HEICs, and HE-Coatings for potential applications are summarized.