Phase Selection in High-Entropy Alloys

The high mixing entropy of high-entropy alloys usually leads to the formation of disordered or partially ordered solid solutions in these alloys. It has been observed that disordered solid solution formation in such alloys happens, when elements with similar chemical nature and atomic size are chosen to form the alloys. If the constituent elements in these alloys have significant differences in terms of their atomic sizes or chemical nature, there is a tendency to form partially ordered solid solutions, or even stoichiometric compounds. Under certain conditions, amorphous phases might form. The present chapter attempts to rationalize these observations in terms of various approaches that were developed starting from the Hume-Rothery rules.