Thermodynamic modelling of the Cu-Mg-Zn ternary system.

The quasibinary MgCu2-MgZn2 system was optimized with the program BINGSS. A ll phase diagram data and thermodynamic values available in the literature were critically assessed before the optimization. Experimental investigatio ns by EDX of ternary Cu-Mg-Zn alloys were specifically performed to provide missing data of the Cu solubilities of the Mg-Zn phases. The Laves-phases C15 (MgCu2), C14 (MgZn2) and C36 (tau,Mg2CuZn3) existing in the Cu-Mg, Mg-Z n and Cu-Mg-Zn systems were described by the "Compound-Energy-Formalism" wi th Cu-Zn exchange, Mg(Cu1-xZnx) and a weak tendency for antistructure atom formation (Cu and Zn on the Mg sublattices, Mg on the Cu-Zn sublattices). T he binary intermetallic phases MgZn, Mg2Zn3 and Mg2Zn11 are modelled to hav e Cu-Zn exchange on one sublattice. The Bragg-Williams description of order ing was extended to describe the ternary range of the beta CuZn phase. Esti mates were made, where experimental data are not sufficient. Using the bina ry subsystems from the literature with small updates the Cu-Mg-Zn ternary s ystem was calculated. In general, good agreement is obtained between calcul ations and experiments.