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

•A method was proposed to prepare Si crystals via directional solidification.•Mechanistic insight into enrichment of Si crystals was sought.•The effect of electromagnetic stirring on the enrichment of Si was analyzed.•The effect of pulling rate on the enrichment of Si was analyzed.•A lower pulling rate is beneficial for the enrichment and separation of Si. 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.