NEW THERMODYNAMIC DATA FOR LIQUID ALUMINUM-MAGNESIUM ALLOYS FROM EMF,VAPOR-PRESSURES, AND CALORIMETRIC STUDIES

Experimental thermodynamic studies of liquid Al-Mg alloys have been pe rformed by several methods resulting in: (1) Mg activities from galvan ic cells with liquid electrolytes at temperatures from 910 to 1070 K, at X-Mg, = 0.1 to 0.7 and for the dilute range when X-Mg = 0.0126 to 0 .1430 at 927 K; (2) Mg activities from the emf method with solid CaF2 electrolyte at temperatures 921 to 1093 K, with concentrations X-Mg = 0.05 to 0.9; (3) Mg activities from vapor pressure measurements (Knuds en effusion method) at temperatures ranging from 722 to 1188 K, at X-M g = 0.0424 to 0.8885. Vapor pressures of pure solid Mg at temperatures 674 to 851 K. In addition, liquidus temperatures for Mg-and Al-rich a lloys were obtained; and (4) Partial and integral enthalpies from reac tion calorimetry at 1023 K, starting from pure Mg bath at concentratio ns, X-Al = 0.066 to 0.499, and starting from pure Al bath at X-Mg = 0. 522 to 0.996. The mutual consistency of these four sets of data was an alyzed. New results together with the selected thermodynamic informati on reported in literature were optimized to describe the liquid phase with the Redlich-Kister equation, as a preliminary step for phase diag ram calculations of the Al-Mg system.