Thermodynamic re-modeling of the Co–Gd system

Abstract

Abstract The Co–Gd system was re-assessed using the CALPHAD technique. The solution phases (liquid, body-centered cubic, face-centered cubic and hexagonal close-packed) were described by the substitutional solution model. The temperature dependence of the interaction parameters of the liquid phase was separately expressed by the linear function and Kaptay equation. The intermetallic compounds Co17Gd2 and Co5Gd, which have the same CaCu5-type structure, were treated as one phase and described by a three-sublattice model (Co2, Gd)(Co2, Gd)2Co15, with Co2 and Gd mixing on the first and second sublattices and the third sublattice occupied by Co. The other compounds (Co7Gd2, Co3 Gd, Co2Gd, Co3Gd4 and CoGd3) were treated as stoichiometric compounds. Two sets of self-consistent thermodynamic parameters of the Co–Gd system were obtained.