A thermodynamic assessment of the copper–gallium system

Abstract

A thermodynamic assessment of the Cu–Ga system was carried out by the CALPHAD approach (CALculation of PHase Diagram). The liquid phase, the solid solution phases of fcc ( α -Cu), bcc ( β ) and hcp ( ζ ), the solution compounds of Cu 9Ga 4_0 ( γ 0 ), Cu 9Ga 4_1 ( γ 1 ), Cu 9Ga 4_2 ( γ 2 ) and Cu 9Ga 4_3 ( γ 3 ), the stoichiometric compounds of Cu 0.778Ga 0.222 ( ζ ′ ) and CuGa 2, and the terminal phase of orthorhombic-Ga were taken into consideration in the optimization. The substitutional solution model was used for the liquid phase and the solid solution phases of fcc, bcc and hcp. The solution compounds related to Cu 9Ga 4 were described with the sublattice model. The order–disorder transformation between Cu 9Ga 4_0 ( γ 0 ) and Cu 9Ga 4_1 ( γ 1 ) was considered. In the model description of Cu 9Ga 4_2 ( γ 2 ) and Cu 9Ga 4_3 ( γ 3 ), vacancies were considered. Differential scanning calorimetric analysis was conducted to obtain phase transformation temperatures and the enthalpies of fusion of Cu–Ga alloys. A set of self-consistent thermodynamic parameters were obtained and the calculated phase diagram and thermodynamic properties were presented and compared with experimental data.