Thermophysical properties of Al-Cu liquid alloys

Considerable effort is permanently directed to optimise methods and facilities for material processing technologies like melting, refining or casting of metallic alloys. The main goals are an improvement of the final product quality, an enhancement of the process efficiency and an economical consumption of resources and energy. Nowadays it is impossible to imagine such optimisation without performing numerical simulations and a corresponding physical modelling. However, the accuracy of the predictions depends sensitively on the availability of precise and trustworthy data concerning the thermophysical properties of the alloys under consideration. The development of new workable aluminium-based light alloys is a key issue in current materials science. Al-Cu alloys, for instance AlCu₄TiMg (A356), are the most utilized casting alloys in the aluminium industry. The distinctive characteristics of these alloys are low density, high melting temperature, good thermal conductivity and excellent oxidation resistance.
In this work, thermophysical properties (density, viscosity and electrical conductivity) of liquid Al₉₆Cu₄, Al₈₀Cu₂₀, Al₇₀Cu₃₀, and AlCu₄TiMg (wt.%) alloys have been measured in a wide temperature range from the melting point up to 1200 K. Corresponding fit relations have been derived for the density, the dynamic viscosity and the electrical conductivity. All properties are compared to available literature data. An increase of a copper content raises gradually the density and the dynamic viscosity of aluminium suggesting a short-range order in the liquid state. According to the density and viscosity data, no substantial structure rearrangement takes place with admixtures. At the same time, the electrical conductivity results demonstrate that small additions of copper slightly raise the conductivity of liquid Al, while further increase of a copper content decreases predictably the conductivity values.