Experimental Investigation and Simulation of Al–Si Casting Microstructure Formation

Abstract

The aim of the present study is to investigate the influence of thermal variables on the as-cast microstructure of hypoeutectic and eutectic Al–Si alloys and to establish correlation between the solidification thermal parameters and interparticle spacing for Al–12%Si alloy during the unidirectional solidification. New relationships are suggested based on the image processing programs in order to accurately quantify the microstructure evolution. A numerical approach is developed to quantitatively determine solidification thermal variables such as growth rate (interface velocity), temperature gradient, cooling rate, and local solidification time. The experimental microstructure measurements are combined with numerical solutions using finite difference (FD) and control volume (CV) methods, and models are obtained for this structure with solidification parameters. Applying image processing program with relationships suggested in this study gives more accuracy to compute interparticle spacing compared with conventional methods. For Al–12%Si alloys, which are widely used, the dispersion of the phases must reflect both decreasing interface velocity and temperature gradient as the microstructure is examined from the chilled surface towards the riser, thus, increasing coarseness of the microstructure caused by both factors.