Solid-solution phase formation rules for high entropy alloys: A thermodynamic perspective

To save time and money before starting the production of a high entropy alloy (HEA), it is important to predict the possibility of HEA formation and the probable final microstructure using the solid solution phase formation thermodynamic rules. In this research, a step-by-step calculation of thermodynamic parameters is conducted to predict the possibility of formation and determine the final properties such as ∆Hmix, ∆Smix, δr, δχ, Ω, VEC, and Tm for three Ni20Co20Cu15Fe20Mn25, Ni35Co20Cu5Fe5Mn35, and Ni5Co5Cu35Fe35Mn20 HEAs. Based on the obtained results, it is not possible to form a HEA with a solid solution structure for the Ni35Co20Cu5Fe5Mn35 and Ni5Co5Cu35Fe35Mn20 systems due to a low ∆Smix value of 11.28 J.mol^-1.K^-1. Based on the calculated values of ∆Hmix, intermetallic compound formation and segregation are predicted for Ni35Co20Cu5Fe5Mn35 and Ni5Co5Cu35Fe35Mn20, respectively.