Thermodynamic study of liquid Cu-Mg alloys by vapor pressure measurements

Abstract

Thermodynamic properties of liquid Cu-Mg alloys have been determined by magnesium vapor pressure measurements over pure liquid magnesium and liquid Cu-Mg alloys, in the composition range of 11 to 90 mole pct Mg between 845 and 1345 K, employing the transpiration technique. Based on the quadratic formalism suggested by Turkdogen and Darken for binary systems, analytical expressions have been derived representing integral and partial molar thermodynamic properties as functions of composition for the two terminal regions of N_Mg=0 to 0.33 and 0.6 to 1.0. From the measured activity values of magnesium and copper, in the liquid alloys in equilibrium with solid intermetallic compounds, standard free energies of formation of Cu₂Mg(s) and CuMg₂(s) relative to pure solid components have been calculated and expressed as functions of temperature.