Thermodynamics of liquid aluminium-copper-germanium alloys

Partial for aluminium and integral enthalpies of mixing of liquid Al-Cu-Ge alloys have been measured by high-temperature isoperibolic calorimetry at T = (1380 +/- 5) K. Thermodynamic activities, partial for aluminium and integral Gibbs free energies of mixing have been determined by the electromotive force method (emf) over the range 1050 less than or equal to T/K less than or equal to 1250. Integral excess entropies of mixing have been calculated from calorimetric enthalpies and emf measured Gibbs free energies of mixing. The integral enthalpies of mixing and the integral excess Gibbs free energies of mixing have been also evaluated based on the literature data for boundaries using the Bonnier geometric model. Differences between experimental and calculated thermodynamic functions of mixing are positive. These facts as well as negative excess integral entropies of mixing reveal information about micro segregation in the melt. Therefore, the existence of ternary eutectic has been forecasted for Al-Cu-Ge phase diagram. (C) 2003 Elsevier Ltd. All rights reserved.