Experimental investigation and thermodynamic modeling of phase equilibria in the Ag-Ni-Zr ternary system

The phase equilibria of the Ag-Ni-Zr ternary system were investigated based on the key experiments coupled with thermodynamic modeling. Thirty ternary alloys were prepared to determine the isothermal sections of the Ag-Ni-Zr system at 500, 700 and 900 °C, respectively, by means of X-ray diffraction (XRD) and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (SEM/EDS). Based on the thermodynamic descriptions of three binary systems available in the literature as well as the experimental phase equilibrium data obtained from the present work, ten three-phase regions were determined. No ternary compound was found. The maximum solubilities of Ag in the Ni-Zr binary compounds and Ni in the Ag-Zr binary compounds were measured. The substitutional model and sublattice model were used to describe the solution phases and intermediate phases, respectively. Based on the thermodynamic descriptions of three constituent binary systems as well as the experimental phase equilibrium data obtained from the present work, a thermodynamic assessment of the Ag-Ni-Zr system was carried out using the CALPHAD (CALculation of PHAse Diagrams) approach. A set of thermodynamic parameters were obtained and the isothermal sections of the Ag-Ni-Zr system were calculated. The calculated results agree well with the experimental data.