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 li quid phase which extends from the binary system Pb-Zn. The calculated isothermal sections at 714, 757, 805, 842 and 877 K, in which two liqu id phases are shown to exist in equilibrium with each other, will be p resented and compared with experimental data. The calculated activitie s of Zn in the liquid phase for different isopleth sections are in goo d agreement with experimental data. The appearance of GP Zones in Al-C u-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 o btained for the binary AI-Cu system and then extended into the ternary to describe the precipitation of GPZB zones. The Thermo-Calc calculat ion package was used for this purpose.