Thermodynamics of liquid aluminium–copper–silicon alloys

In this paper, thermodynamic properties of liquid Al–Cu–Si alloys were studied by electromotive force method with liquid electrolyte at 920–1250 K and by high-temperature isoperibolic calorimetry at 1750±5 K. The integral enthalpy of mixing in ternary Al–Cu–Si melts was estimated by Bonnier model for definition of boundary binary systems contribution to ternary alloys thermodynamics. The satisfactory agreement between experimental and estimated data demonstrates that thermodynamic properties of ternary liquid alloys are mainly defined by thermodynamic behaviour of boundary binary systems. Analysis of concentration and thermal dependencies of thermodynamic functions of mixing in liquid Al–Cu–Si alloys has been performed. It has been established that increasing of temperature results in decreasing of the integral enthalpy of mixing. This fact is probably associated with contribution of silicon clusters into ternary alloys thermodynamics.