Thermodynamic modeling of Cu–Ni–Y system coupled with key experiments

Abstract

A complete thermodynamic description of the Cu–Ni–Y ternary system has been obtained using the CALPHAD (CALculation of PHAse Diagram) approach. Ternary solubility of the third element in the binary compounds in the Cu–Ni–Y system is described using sublattice model within the compound energy formalism (CEF) to take into account the recently reported experimental solubility ranges. The modified quasi-chemical model (MQM) has been used to describe the liquid phase in order to account for the presence of short range ordering properly. To study the melting behavior of the Cu–Ni–Y alloys and to verify the consistency of the thermodynamic model with experimental results, 10 key samples were prepared and the phase transformation temperatures were measured using differential scanning calorimeter (DSC). The microstructural characterization and crystallographic analysis of the alloys were carried out using scanning electron microscopy (SEM) coupled with WDS analysis and X-ray diffraction (XRD). Several vertical sections, liquidus projection and isothermal section at 973 K have been calculated and found to be in good agreement with the current experimental data as well as with the literature.