Experimental study on interaction of fluid flow and solidification in Al-Si-Cu alloys

A hypoeutectic Al-6Si-4Cu (wt-%) alloy was used in the present study to investigate the effect of controlled fluid flow conditions on the microstructure formation in cast Al alloys experimentally. The alloy has been directionally solidified upwards under a medium temperature gradient (3 K mm(-1)) in an aerogel based furnace facility over a range of constant solidification velocities (0.015-0.15 mm s(-1)). A coil system around the sample induces a homogeneous rotating magnetic field being able to generate a controlled fluid flow in the melt. The application of rotating magnetic fields during directional solidification results in a strong segregation effect: for high magnetic induction and therefore high fluid flow velocity an enrichment of solute is observed at the axis of the sample. The primary dendrite spacing decreases whereas the secondary dendrite arm spacing increases with increasing magnetic induction, clearly revealing the effects of convections on solidification kinetics.