A thermodynamic assessment of the copper–gallium system

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 (αα-Cu), bcc (ββ) and hcp (ζζ), the solution compounds of Cu9Ga4_0 (γ0γ0), Cu9Ga4_1 (γ1γ1), Cu9Ga4_2 (γ2γ2) and Cu9Ga4_3 (γ3γ3), the stoichiometric compounds of Cu0.778Ga0.222 (ζ′ζ′) and CuGa2, 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 Cu9Ga4 were described with the sublattice model. The order–disorder transformation between Cu9Ga4_0 (γ0γ0) and Cu9Ga4_1 (γ1γ1) was considered. In the model description of Cu9Ga4_2 (γ2γ2) and Cu9Ga4_3 (γ3γ3), 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.