Mixing Enthalpies of Liquid Ag-Mg-Pb Alloys: Experiment vs. Thermodynamic Modeling

A drop calorimetric method was used to measure liquid Ag-Mg-Pb alloys. The partial and integral mixing enthalpies of the investigated alloys were determined at a temperature of 1116 K. The experiments were performed for four separate series starting from binary alloys with a constant x_Mg/x_Pb ratio of 1/3, 1, 3 ((Mg_0.25Pb_0.75)_1-xAg_x, (Mg_0.50Pb_0.50)_1-xAg_x, (Mg_0.75Pb_0.25)_1-xAg_x) and x_Ag/x_Mg ratio of 1/3 (Ag_0.25Mg_0.75)_1-xPb_x. Next, the ternary interaction parameters were determined using the Muggianu model, the thermodynamic properties of binary systems in the form of the Redlich-Kister equations and the values of the mixing enthalpy changes, which were determined in this study. The partial mixing enthalpies of Ag, Mg, and Pb were calculated based on the binary and elaborated ternary interaction parameters for the same intersections in which the measurements were conducted. It was found that the ternary Ag-Mg-Pb liquid solutions are characterized by negative deviations from the ideal solutions, with a maximal value slightly lower than -13 kJ/mol for alloys with the ratio (Mg_0.75Pb_0.25) and x_Ag = 0.4166.