Thermodynamic description of the stable Pb-Sn-Zn and the metastable Al-Cu-Mg miscibility gaps

The ternary system Pb-Sn-Zn displays a large miscibility gap in the liquid phase which extends from the binary system Pb-Zn. The calculated isothermal sections at 714, 757, 805, 842 and 877 K, in which two liquid phases are shown to exist in equilibrium with each other, will be presented and compared with experimental data. The calculated activities of Zn in the liquid phase for different isopleth sections are in good agreement with experimental data. The appearance of GP Zones in Al-Cu-Mg alloys may be described by a Gibbs energy function which predicts a miscibility gap in the fee (Al) phase. The new function was first obtained for the binary AI-Cu system and then extended into the ternary to describe the precipitation of GPZB zones. The Thermo-Calc calculation package was used for this purpose.