On the local microstructural characteristics observed in sand cast Al–Si alloys

The aim of this work is to explore the phenomenology that describes the local solid formation and heat transfer occurring during sand cast alloys solidification in order to propose an explanation to the observed changes of local microstructural characteristic lengths in hypoeutectic and eutectic Al–Si based alloys. Microstructural observations are made in different radial positions of solidified rod castings. Also, solidification kinetics information is obtained using the Fourier thermal analysis method. A coupled heat transfer-solidification kinetics model is employed to predict the thermal history, the solidification kinetics and some microstructural parameters in order to compare the predictions with experimental results. The model and the experimental outcome suggest that there is a strong dependence of the local solidification kinetics on the local heat transfer. The analysis of this dependence is used to propose an explanation to the observed changes in microstructural characteristics at different locations within sand castings.