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 < x(Sm) < 0.15; 0.37 < x(Sm) < 1), Sm-Sn (0 < x(Sn) < 0.13; 0.56 < x(Sn) < 1) alloys and ternary Al-Sm-Sn alloys (along the three concentration sections: (Sm0.87Sn0.13)(1-x)Al-x (0 < x < 0.32); (Sm0.44Sn0.56)(1-x)Al-x (0 < x < 0.12); (Al0.85Sm0.15)(1-x)Sn-x (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 +/- A 0.5 kJ/mol at x(Sm) = 0.35 (T = 1500 K, undercooled melt), Sm-Sn is -67.7 +/- A 0.5 kJ/mol at x(Sn) = 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.