Phase equilibria in the Au-Cu-In ternary at 500°C: Experimental study and CALPHAD modeling

Phase equilibria of the Au-Cu-In system are investigated by combination of key experiments and thermodynamic modeling. Partial isothermal section at 500 degrees 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 alpha, gamma and eta' phases were measured by DTA/DSC. Thermodynamic assessment of the Au-Cu-In ternary system is performed by CALPHAD method using Thermo-Calc (R) software. Thermodynamic properties of disordered fcc, liquid and zeta 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 gamma phase in Au-In and Cu-In edges. For the gamma, alpha, and eta' phases sublattice models were used. Good agreement with our experimental data for both calculated phase equilibria and non-equilibrium solidification curves was achieved.