Thermodynamic properties of liquid (magnesium + copper) alloys by vapour-pressure measurements made by a boiling-temperature method

Abstract

Measurements have been made of the equilibrium vapour pressures over pure Mg(I) and {xMg + (1 - x)Cu}(l) with x from 0.90 to 0.17 in the temperature range 955 to 1250 K by the boiling-temperature method. Thermodynamic activities of Mg in the alloys and those of Cu derived by the graphical Gibbs-Duhem integration are found to exhibit large negative deviations from ideality over the entire composition range. Further, the molar enthalpies of mixing and excess molar entropies are negative. The standard molar Gibbs free energies of formation of solid MgCu₂(β) and Mg₂Cu(γ) intermediate phases have been calculated from the experimental results and are compared with the values reported in the literature.