Effects of solidification parameters and magnetic field on separation of primary silicon from hypereutectic Ti–85 wt.% Si melt

Abstract

In the present study, the effects of the solidification parameters and magnetic field on the enrichment of primary Si via separation of a hypereutectic Ti–85 wt.% Si alloy during directional solidification were experimentally investigated. The results indicated that increasing the pull-down rate from 5 to 15 μm/s increased the temperature gradient and growth rate at the same position of the ingot, although the Si content decreased. At a certain pull-down rate (e.g., 5 μm/s), with the increasing thickness of the Si-rich layer, the temperature gradient, growth rate, and Si content all decreased. In presence of a magnetic field, the solidification direction produced an electromagnetic force, which acted on the tip of the dendrite and changed the shape of the separation interface. Meanwhile, the electromagnetic stirring enhanced mass transfer at pull-down rates of 5, 10, and 15 μm/s, while dendritic breakdown processes maintained corresponding enrichment layer thicknesses of 45 mm, 35 mm, and 15 mm, respectively. The results could be helpful for expanding the applications of Ti–Si alloys and solving the problems presented by the solid waste of Ti-BF slag, i.e., environmental pollution and wastage of Ti resources.