Phase equilibria in the Au–Cu–In ternary at 500оC: Experimental study and CALPHAD modeling

Abstract Phase equilibria of the Au–Cu–In system are investigated by combination of key experiments and thermodynamic modeling. Partial isothermal section at 500 °C of the Au–Cu–In system for In content up to 40 at.% have been plotted experimentally using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction (XRD). The solubilities of the foreign elements in the phases of binary systems are measured. No ternary compounds were found. The temperatures of solidus and/or liquidus of α, γ and η′ phases were measured by DTA/DSC. Thermodynamic assessment of the Au–Cu–In ternary system is performed by CALPHAD method using Thermo-Calc® software. Thermodynamic properties of disordered fcc, liquid and ζ phases were described by Redlich-Kister-Muggianu model, though the Toop extrapolation was also tested. The description of the Au–In binary was modified to account for the change in stability parameters of fcc In, and for unifying the models of the γ phase in Au–In and Cu–In edges. For the γ, α, and η′ phases sublattice models were used. Good agreement with our experimental data for both calculated phase equilibria and non-equilibrium solidification curves was achieved.