Thermodynamics of the liquid Co-Cu system and calculation of phase diagram

Abstract

Knudsen-cell mass spectrometric measurements have been carried out in the liquid phase of the Co-Cu system in the concentration range 25.0 to 85.9 at. % Cu in the temperature range 1347 to 1587 °C. The molar excess Gibbs energy, enthalpy and entropy of mixing, as well as the thermodynamic activities of components in the liquid Co-Cu system were determined using the composition and temperature dependence of the ratio of intensities of ⁵⁹Co and ⁶³Cu ions. The results show that a subregular solution model would fit measured data well (2-parameter thermodynamically adapted power (TAP) series: C ^H _n in J·mol⁻¹; C ^H₁ =35,961, C ^H₂ =−5573.2; C ^S _n in J·mol^−1·K−1; C ^S₁ =5.54, C ^S₂ =−3.35). A special experiment verified solid-liquid phase equilibrium at 1327 °C and the phase diagram was calculated.