Systematical assessment of phase equilibria and thermodynamic properties in the RE (rare earth metals)—Cu binary systems

Abstract In this work, seven RE–Cu (RE = Ce, Pr, Sm, Eu, Tb, Er and Lu) binary systems were optimized using the CALPHAD method based on the reported experimental data. The liquid phase and terminal solid solution phases were modeled using the substitutional solution model, while the intermetallic compounds were treated as stoichiometric compounds. Self‐consistent thermodynamic parameters of seven RE–Cu binary systems were obtained, which can be used to reproduce the experimental results including phase diagram and thermodynamic properties. Furthermore, in combination with the reported assessments of six RE–Cu (RE = La, Nd, Gd, Dy, Ho, and Yb) binary systems, phase equilibria, and thermodynamic properties of 13 RE–Cu (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu) binary systems were examined systematically. Generally, it was observed that as the RE atomic number increases, the formation temperatures of the RE–Cu intermetallic compounds increase gradually, and the enthalpy of mixing of liquid RE–Cu alloys and the enthalpy of formation of the RE–Cu intermetallic compounds become increasingly negative. These results provide a comprehensive set of thermodynamic parameters for the RE–Cu binary systems, which will serve as a crucial foundation for developing a thermodynamic database of RE–Cu‐based alloys.