Thermodynamic and dynamical properties of liquid Al-X (XÂ =Â Sn, Ge, Cu) systems

A study of thermodynamics and dynamical properties of liquid Al-Sn, Al-Ge and Al-Cu alloys at different temperatures have been made within the frame of the Quasi-Lattice Theory (QLT) using the Flory's model. Assuming the order energy parameters as temperature dependent, the composition dependence of viscosity, η, and various thermodynamic properties such as the free energy of mixing, enthalpy of mixing, entropy of mixing and activity coefficient of the liquid alloys have been calculated. The roles of size differences between constituent species in the alloys were examined. The study reveals that the order energy parameter ω is positive for Al-Sn alloys indicating existence of self-coordination of atoms across the composition range, while negative values of ω for Al-Ge and Al-Cu alloys suggest a tendency of compound formation (preference for unlike atoms to pair as nearest neighbor) in their liquid state. The study also shows that Al-Sn is a weak interacting system. This fact is further justified by the results of the estimated dynamical properties with a reasonable agreement between the calculated results and corresponding experimental data.