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 Ni۲۰Co۲۰Cu۱۵Fe۲۰Mn۲۵, Ni۳۵Co۲۰Cu۵Fe۵Mn۳۵, and Ni۵Co۵Cu۳۵Fe۳۵Mn۲۰ HEAs. Based on the obtained results, it is not possible to form a HEA with a solid solution structure for the Ni۳۵Co۲۰Cu۵Fe۵Mn۳۵ and Ni۵Co۵Cu۳۵Fe۳۵Mn۲۰ systems due to a low ∆Smix value of ۱۱.۲۸ J.mol-۱.K-۱. Based on the calculated values of ∆Hmix­, intermetallic compound formation and segregation are predicted for Ni۳۵Co۲۰Cu۵Fe۵Mn۳۵ and Ni۵Co۵Cu۳۵Fe۳۵Mn۲۰, respectively.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 Ni۲۰Co۲۰Cu۱۵Fe۲۰Mn۲۵, Ni۳۵Co۲۰Cu۵Fe۵Mn۳۵, and Ni۵Co۵Cu۳۵Fe۳۵Mn۲۰ HEAs. Based on the obtained results, it is not possible to form a HEA with a solid solution structure for the Ni۳۵Co۲۰Cu۵Fe۵Mn۳۵ and Ni۵Co۵Cu۳۵Fe۳۵Mn۲۰ systems due to a low ∆Smix value of ۱۱.۲۸ J.mol-۱.K-۱. Based on the calculated values of ∆Hmix­, intermetallic compound formation and segregation are predicted for Ni۳۵Co۲۰Cu۵Fe۵Mn۳۵ and Ni۵Co۵Cu۳۵Fe۳۵Mn۲۰, respectively.

Keywords:

High entropy alloy , Thermodynamic parameters , Solid solution , Phase formation , Segregation , Intermetallic compound