Using a Calvet type calorimeter, the enthalpy of mixing in the two ternary systems, Al-Sn-Zn and Ag-Sn-Zn was determined at 973 K. In the Al - Sn - Zn system, the investigations were carried out along three cross-sections with constant molar ratios of Sn: Zn = 1 : 2, 1 : 1 and 2: 1 and an aluminium content between 0 and 100 at.%. For the Ag-Sn-Zn system, the measurements have been done at constant molar ratios of Ag: Sn = I : 3, 1 : 1 and 3: 1 with zinc contents between 0 and 50 at.%.. The substitutional solution model of Redlich-Kister according to the CALPHAD method was used for a least-square fit of the experimental data in order to get an analytical expression for the integral enthalpy of mixing. The ternary extrapolation models of Kohler, Muggianu, and Toop were applied on the binary data to compare measured, fitted, and extrapolated values.
