Solid solution phases and their microstructures in HEAs

High-entropy alloys (HEAs), being multicomponent equiatomic or near equiatomic in nature, have a high mixing entropy. They have a strong tendency to form disordered and partially ordered solid solutions instead of stoichiometric intermetallic compounds or strong elemental segregation, when they are prepared through various processing routes. Most of the HEAs have FCC or BCC structures, while a few HEAs have shown the formation of HCP structures. Under certain conditions, when the interactions between some constituent elements differ a lot with others in nature, the formation of intermetallic compounds or elemental segregation has been observed because mixing entropy effect is not sufficient to mix them with larger mutual solubility. The present chapter gives a comprehensive account of solid solution formation in HEAs.