TEMPERATURE–COMPOSITION DEPENDENCE OF THERMODYNAMIC MIXING FUNCTIONS OF Co–Cr–Cu–Fe–Ni MELTS

Abstract

In the framework of the CALPHAD method, a thermodynamic database was developed for calculating the thermodynamic properties of liquid alloys in the Co–Cr–Cu–Fe–Ni system and its quaternary subsystems. The thermodynamic mixing functions of the melts were calculated at 1873 and 1500 K. The calculated excess integral mixing functions showed positive values in most of the composition space of the four-component systems with copper and the Co–Cr–Cu–Fe–Ni system. The ideal contribution to the Gibbs energy of mixing for four- and five-component melts of the Co–Cr–Cu–Fe–Ni system was predominant. The excess Gibbs energy of mixing for equiatomic liquid alloys of four-component systems with copper and the Co–Cr–Cu–Fe–Ni system was lower in magnitude than the ideal component of the Gibbs mixing energy. With decreasing temperature, the positive deviations from the ideal behavior of the excess Gibbs mixing energy increased and the magnitude of the ideal Gibbs mixing energy decreased, resulting in lower thermodynamic stability of the liquid phase. The calculated separation temperatures for four- and five-component equiatomic Co–Cr–Cu–Fe–Ni melts varied in the 1370–1770 K range. The highest liquid-phase separation temperatures were observed in the melts containing both copper and chromium.