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

Abstract

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 twophase 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.

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

“…Based on the experimental data obtained from the present work and the literature, the thermodynamic parameters of the Ag-Ni-Zr system were evaluated by the optimization module PARROT of the Thermo-Calc program, 43 which works by minimizing the square sum of the differences between the measured and calculated values. The step-by-step optimization procedure 44,45 was utilized in the present assessment. In the optimization process, the weight of each piece of experimental information was varied systematically until most of the experimental data were accounted for within the estimated uncertainty limits.…”