Microstructural evolution caused by electromagnetic stirring in superheated AlSi7Mg alloys

The microstructure of the supercooled slurry obtained by the traditional electromagnetic stirring (EMS) process easily deteriorates during transferring. In order to inhibit this deterioration, the present work in discussing the microstructural evolution suggests that the EMS process can be conducted above the liquidus of alloy, i.e., through superheated + EMS. In this context, it is of particular interest to see the effects of the superheated + EMS process on the morphology and size distribution of α-Al phase and eutectic silicon obtained by the subsequent pouring at different superheated temperatures. It is concluded that the superheated + EMS process not only refines the α-Al phase and alters its morphology to a rosette or near-spherical shape, but also refines the eutectic silicon particles. Two hypotheses that could lead to such an effect are raised, i.e., thermal fluctuation homogenization and Si agglomeration.