Computation of the thermodynamic parameters of Sm–Co–Fe ternary alloys

Abstract This study evaluated the thermodynamic parameters of Sm–Co, Sm–Fe and Co–Fe binary alloys using the Miedema model. The Miedema and Toop models were then combined to obtain the mixing enthalpy (Δ H ), excess entropy ( S E ), excess Gibbs free energy ( G E ) and activity ( α ) of Sm–Co–Fe ternary alloys. The findings indicate that the Δ H , S E and G E values of all binary alloys were negative. The Co and Fe elements have similar properties are similar, but they are different from Sm elements. Moreover, the Δ H , S E and G E values of the ternary alloys were negative at all molar fractions x i ( i = Sm, Co or Fe), with the minimum values of Δ H , G E , S E being −15.3139, −20.2879 and −2.6556 J molK −1 at x Sm = 46%, x Co = 54% and x Fe = 0%. The iso-activity curves illustrated a marked reduction in the activities of Sm, Co and Fe as their mole fractions decreased. Furthermore, Sm and Co exhibited lower activities within the ternary alloys than Fe, indicating that these elements more likely formed intermetallic compounds than Fe. This study provides important insights into the thermodynamics of Sm–Co–Fe ternary alloys and guides the development of ternary alloys.