Separation and enrichment mechanism of C54–TiSi2 from hypoeutectic Ti–65 wt.% Si alloy during directional solidification via alternating electromagnetic fields

Abstract

The effects of directional solidification parameters and the coupling of directional solidification parameters and alternating electromagnetic fields on separation and enrichment of the C54–TiSi2 phase were investigated in a directionally solidified hypoeutectic Ti–65 wt.% Si alloy. The results indicated that by increasing the pull-down velocity at a given position within the ingot, the cooling rate, growth rate, and temperature gradient of ingot could be increased. At a pull-down velocity near 5 μm/s, the temperature gradient, cooling rate, and growth rate decreased with increasing the thickness of the C54–TiSi2-rich layer. Electromagnetic fields enhanced mass transfer at pull-down velocities of 5, 10, 15, and 20 μm/s, with resulting enriched layer thicknesses of 15, 10, 10, and 5 mm, respectively. By increasing the percentage of Ti in the Ti–Si alloy from 25 to 35 wt.%, the thickness of the C54–TiSi2-rich layer was increased from 2.5 to 3.3 cm. However, the maximum C54–TiSi2 content obtained experimentally in this layer decreased from 92.06 to 79.49 mass%.