The role of the eutectic in porosity formation in Al-Si foundry alloys

It is now well-established that there are three different possible eutectic solidification patterns in Al-Si foundry alloys. Furthermore, the operation of each solidification mechanism can be manipulated through additions of typical modifier elements, such as Sr and Na, but also less common elements. The spatial distribution of evolving eutectic is very different for each eutectic solidification pattern, resulting in large differences in feedability in the last stages of solidification because of changes in permeability and isolation of liquid pockets. This paper presents a coherent approach to solidification mechanisms in Al-Si alloys and the relationship to the porosity formation in this important alloy system.