Effect of a transverse magnetic field on primary-Si distribution during directional solidification in hypereutectic Al-Si alloy

The effect of a transverse magnetic field on the distribution of the primary Si in a directionally solidified Al-21 wt.% Si alloy is investigated. The results reveal that the application of the magnetic field leads to the appearance of banded structures of primary Si. Furthermore, the inclination of the banded structure decreases with the increase of magnetic-field intensity. The in situ measurement results of the Seebeck signal confirm the existence of a thermoelectric power difference between the solid phase and the liquid phase at the solid/liquid interface in the directionally solidified Al-21 wt.% Si alloy. Thus, the formation of the banded structures should be attributed to the thermoelectric magnetic convection (TEMC) and the resultant force of the primary Si, i.e., gravity force and thermoelectric magnetic force (TEMF). The migration of the primary Si toward the lower left side of the sample is induced by the resultant force, which leads to the formation of banded structures. Moreover, the increase of magnetic-field intensity increases the resultant force of the primary Si, resulting in a decrease of the inclination of banded structure.