Thermodynamic evaluation of the Co–Sc and Fe–Sc systems

The thermodynamic assessments of the Co–Sc and Fe–Sc binary systems were carried out by using the CALPHAD (Calculation of Phase Diagrams) method on the basis of the experimental data including the thermodynamic properties and phase equilibria. The Gibbs free energies of the liquid, bcc, fcc, and hcp phases were described by the subregular solution model with the Redlich–Kister equation, and those of the intermetallic compounds (Co2Sc, CoSc, CoSc2, CoSc3, αFe2Sc, βFe2Sc, λFe2Sc and Fe6Sc29) in these two binary systems were described by the sublattice model. The thermodynamic parameters of the Co–Sc and Fe–Sc binary systems were optimized for reproducing the experimental data on phase diagrams and thermodynamic properties, and an agreement between the calculated results and experimental data was obtained in each binary system.