Impact of inlet flow on macrosegregation formation accounting for grain motion and morphology evolution in DC casting of aluminium

Abstract

Several transport mechanisms contribute to macrosegregation formation in Direct Chill (DC) casting of aluminium. The latter include solidification shrinkage induced flow, thermal-solutal convection and grain motion. The relative importance of these transport mechanisms depends on process parameters such as cast velocity, inlet melt flow, cooling rate, cast dimensions etc. Of these, the inlet melt flow due to vertical jet is known to cause significant modification in macrosegregation by resuspending equiaxed grains at the center of the ingot/billet. In this paper, we investigate by means of modeling the macrosegregation formation due to an inlet vertical jet. For this purpose, a three-phase, multiscale solidification model accounting for above mentioned transport phenomena except for shrinkage induced flow is applied on a DC cast billet. The model considers grain motion accounting for both globular and dendritic equiaxed grain growth and we investigate their interaction with the inlet vertical jet. We show that an interplay of morphology evolution of equiaxed grains and inlet vertical jet together contribute to grain resuspension which in turn modifies macrosegregation formation. We also compare these results with a case with open inlet.