Experimental investigation and thermodynamic calculation of the phase equilibria in the Cu-Mo-Ni ternary system

The phase equilibria at 900 °C, 1000 °C, 1100 °C, 1200 °C and 1300 °C in the Cu-Mo-Ni system were experimentally determined by means of optical microscopy (OM), electron probe microanalyzer (EPMA) and X-ray diffraction (XRD) on the equilibrated alloys. The experimental results firstly found that the fcc-type miscibility gap exists at 900 °C, 1000 °C, 1100 °C and 1200 °C in the Cu-Mo-Ni system, and the solubility of Cu in the MoNi phase at 900 °C, 1000 °C, 1100 °C and 1200 °C are about 0.5 at.%, 1.5 at.%, 1.7 at.% and 4.0 at.%, respectively. The as-cast Cu20Mo20Ni60 (at.%), Cu20Mo30Ni50 (at.%), Cu10Mo60Ni30 (at.%), Cu70Mo10Ni60 (at.%), Cu20Mo60Ni20 (at.%) and Cu80Mo10Ni10 (at.%) alloys appear the separated macroscopic morphologies, which are caused by the liquid phase separation on cooling, while the as-cast Cu10Mo25Ni65 (at.%), Cu32Mo5Ni63 (at.%) and Cu30.7Mo6.3Ni63 (at.%) alloys show the homogenous microscopic morphologies. On the basis of the experimental data investigated by the present and previous works, the phase equilibria in the Cu-Mo-Ni system were thermodynamically assessed by using CALPHAD (Calculation of Phase Diagrams) method, and a consistent set of the thermodynamic parameters leading to reasonable agreement between the calculated results and experimental data was obtained.