The effect of main alloying elements on the physical properties of Al–Si foundry alloys

In this study we describe the effect of the main alloying elements Si, Cu and Ni on the thermal properties of hypoeutectic and near-eutectic Al–Si foundry alloys. By means of systematic variations of the chemical composition, the influence of the amount of ‘second phases’ on the thermal conductivity, thermal expansion coefficient, and thermal shock resistance is evaluated. Thermodynamic calculations predicting the phase formation in multi-component Al–Si cast alloys were carried out and verified using SEM, EDX and XRD analysis. The experimentally obtained data are discussed on a systematic basis of thermodynamic calculations and compared to theoretical models for the thermal conductivity and thermal expansion of heterogeneous solids.