Thermodynamic Properties of Alloys of the Binary Al-Sm, Sm-Sn and Ternary Al-Sm-Sn Systems

Mixing enthalpies of the liquid binary Al-Sm (0 < xSm < 0.15; 0.37 < xSm < 1), Sm-Sn (0 < xSn < 0.13; 0.56 < xSn < 1) alloys and ternary Al-Sm-Sn alloys (along the three concentration sections: (Sm0.87Sn0.13)1−xAlx (0 < x<0.32); (Sm0.44Sn0.56)1−xAlx (0 < x<0.12); (Al0.85Sm0.15)1−xSnx (0 < x<0.032)) were determined by an isoperibolic calorimetry technique at 1410-1670 K. Thermodynamic properties of liquid Al(Sn)-Sm alloys were described in the whole concentration range using the model of ideal associated solution. Thermodynamic activities of components of the Al(Sn)-Sm melts demonstrate large negative deviation from the ideal behavior, and the mixing enthalpies are characterized by significant exothermic effects. The minimum value of the mixing enthalpy of the Al-Sm melts is −47.1 ± 0.5 kJ/mol at xSm = 0.35 (T = 1500 K, undercooled melt), Sm-Sn is −67.7 ± 0.5 kJ/mol at xSn = 0.48 (T = 1450 K, undercooled melt). The obtained results were compared with the data from survey of the binary Al(Sn)-Sm systems and with the values calculated by the different models from the data for the binary boundary subsystems of the ternary Al-Sm-Sn system.