Thermodynamic optimization of the Gd-Pb system using random solution and associate models

The Gd-Pb system was critically modeled by means of the CALPHAD technique on the basis of experimental data in the literature. Given the asymmetric shape of the liquidus in the Gd-Pb phase diagram, the associate model for the liquid phase was tested and compared with the substitutional solution model. The results of the optimization show that a better agreement with the available experimental data is obtained by means of the associate model than the substitutional solution model. The solution phases (liquid, bcc, fcc, hcp) were treated with the Redlich-Kister equation. The intermetallic compounds Gd5Pb3, αGd5Pb4, βGd5Pb4, Gd11Pb10, Gd6Pb7, GdPb2, GdPb3 were treated as stoichiometric compounds. Two sets of self-consistent thermodynamic parameters of the Gd-Pb system were obtained.