Development of high entropy alloys (HEAs): Current trends

A novel concept of developing multi-principal elements, or compositional complex alloys is referred as high-entropy alloys (HEAs). This review addresses the role of entropy in alloying additions along with the effect of various elements listed in the periodic table in forming the HEAs. Phase formation rules and the associated parameters along with their significance are discussed. The physical metallurgy technique is elaborated with reference to the high-entropy effect, severe lattice distortion effect, sluggish diffusion effect, and cocktail effects. Various types of HEAs such as light weight HEAs, nanoprecipitate HEAs, ultrafine-grained HEAs, dual-phase HEAS and TRIP/TWIN HEAs are discussed. Further, the effects of mechanical alloying in HEAs are presented. Finally, the microstructural effects and mechanical properties of HEAs are addressed with reference to the published literature.