Effect of melt flow on dendritic growth in AlSi7-based alloys during directional solidification

Abstract

High-strength automotive components are often made of AlSi7-based alloys. A very challenging problem with aluminium casting is the influence of melt flow during solidification, because it affects the microstructure formation and therefore the material properties. The scope of this paper is to investigate the effect of forced melt flow on the evolution of the dendritic microstructure in a binary AlSi7 alloy during directional solidification. Global modelling using the software CrysMAS provides typical flow patterns and velocities. These values are used as boundary condition for the flow in the phase field code MICRESS, which allows the numerical simulation of dendritic array solidification in 2D with applied flow. From solidification experiments in a gradient furnace with applied rotating magnetic field the dendrite shapes are determined. It is found consistently that intense melt flow leads to asymmetric dendrite shapes and the growth behaviour of the dendrite arms is directly correlated with the flow direction.