Experimental study and thermodynamic assessment of the Cu-Ni-Ti system

The Cu-Ni-Ti ternary system has been systematically investigated combining experimental measurements with thermodynamic modeling. With selected equilibrated alloys, the equilibrium phase relations in the Cu-Ni-Ti system at 850 °C were obtained by means of SEM/EDS (Scanning Electron Microscopy/Energy Dispersive Spectrum), EPMA (Electron Probe Micro-Analysis) and XRD (X-ray Diffractometry). Phase transformation temperatures were measured by DSC (Differential Scanning Calorimetry) analysis in order to construct various vertical sections in the Cu-Ni-Ti system. The liquidus projection of the ternary system was determined by the identifying primary crystallization phases in the as-cast alloys and from the liquidus temperatures obtained from the DSC analyses. Based on the available data of the binary systems Cu-Ni, Cu-Ti, Ni-Ti and the ternary system Cu-Ni-Ti from the literature and the present work, thermodynamic modeling of the Cu-Ni-Ti ternary system was performed using the CALculation of PHAse Diagram (CALPHAD) approach. A new set of self-consistent thermodynamic parameters for the Cu-Ni-Ti ternary system was obtained with an overall good agreement between experimental and calculated results.