Thermodynamics of the copper-manganese system - Knudsen-cell mass spectrometric study of the liquid Cu-Mn system and calculation of the phase diagram

Knudsen-cell mass spectrometric measurements have been carried out in the liquid phase of the Cu-Mn system in the concentration range 4.62-73.14 wt.-% Mn in the temperature range 1310-1480 K. The molar excess Gibbs energy, entropy and heal of mixing as well as the thermodynamic activities in the Cu-Mn system were determined using composition and temperature dependence of the ratio of intensities of Cu-63 and Mn-55 ions. The results show that subregular solution model would fit measured data well. The system exhibits positive values of heat of mixing and both positive and negative deviations from ideality for excess Gibbs energy. Based on these data, data in the literature and phase equilibrium data, a thermodynamic assessment of the Cu-Mn system has been made. The new set of parameters was achieved by the CALPHAD method for phase diagram calculation, and from this, the Cu-Mn phase diagram in agreement with published data was generated. (C) Munksgaard, 1996.