Basic Thermodynamic Research of Eutectic High Entropy Alloys Formation

By collecting and summarizing the reported overall composition and phase composition of 18 kinds of eutectic high-entropy alloys (EHEAs), some parameters reflecting their properties were calculated, including mixing enthalpy, mixing entropy, Gibbs free energy, atomic size mismatch, electronegativity difference and valence electron concentration, and the influence of these parameters on the structure of the alloy were analyzed from a thermodynamic point of view. It is found that the calculated mixing entropy equivalent of the overall composition of the eutectic high-entropy alloy basically meets the structural criterion requirements of the traditional high-entropy alloy (such as Delta S-mix >11 J/(mol.K), -15 kJ/mol < Delta H-mix < 5 kJ/mol, delta < 6.6%) to form a single-phase solid solution. But the average free energy of the eutectic phase is lower than the total free energy when the whole forms a single phase, so the eutectic reaction occurs in the solidification process of the eutectic high-entropy alloy forming a multi-phase structure.