Experimental Investigation and Thermodynamic Modeling of the Phase Equilibria in the Cu-Nb-Ni Ternary System

The phase equilibria of the Cu-Nb-Ni system were investigated via a combination of key equilibrated alloys and thermodynamic modeling. Twelve different compositions of ternary alloys were prepared to determine the isothermal sections at 700, 800 and 900 °C, by means of x-ray diffraction and scanning electron microscopy with energy dispersive x-ray spectroscopy. The three- and two-phase regions were determined. The solubilities of the NbNi 3 and Nb 7 Ni 6 phases were measured. No ternary compound was found in this ternary system. Based on the experimental equilibria data from the literature and the present work, a thermodynamic description of the Cu-Nb-Ni system was carried out by using the CALPHAD (CALculation of PHAse Diagrams) method. The substitutional model and sublattice model were employed to describe the solution phases and intermediate phases, respectively. A set of self-consistent thermodynamic parameters of the Cu-Nb-Ni system was conclusively obtained. Most of the reliable experimental data were reproduced by the present thermodynamic modeling.