Verification and Optimization of Single Phase Solid Solution Rule in High Entropy Alloys

High-entropy alloys (HEAs) with single face-centered cubic (FCC) structures always exhibit excellent ductility, and those with a single body-centered cubic (BCC) structure exhibit high strength. The mixture of FCC and BCC structures contributes to a synergy of strength and ductility. Thus, investigating the formation rules of different structures in HEAs is beneficial for obtaining the desired HEA composition. In this article, several HEAs were designed and prepared to verify the pure single-phase solid-solution rule, i.e.,delta < 4.27%, - 7.27 kJ mol(-1) < Delta H-mix < 4 kJ mol(-1)and VEC > 8 for single FCC solid solution and delta < 4.27%, - 7.27 kJ mol(-1) < Delta H-mix < 4 kJ mol(-1)and VEC < 6.87 for single BCC solid solution (atomic size difference:delta, valence electron concentration: VEC, mixing enthalpy: Delta H-mix). Results indicate that the rule can be well applied to the classic HEAs with Delta S-mix > 12.47 J mol(-1) K-1, while for the other HEAs, the critical values of the rule will be extended.