Separation Mechanism of a Si+TiSi ₂ Eutectic Alloy and Metal Impurity Fe Segregation Via Electromagnetic Directional Solidification of Ti-80wt.%Si Alloy Melt

Abstract

The separation mechanism of Si+TiSi₂ eutectic alloy and Fe atom segregation were investigated during the electromagnetic directional solidification of Ti-80wt.%Si alloy melt at pull-down rates from 5 μm/s to 20 μm/s. The experimental results indicated that a fine lamellar Si+TiSi₂ eutectic alloy was obtained in the middle of the ingot after electromagnetic directional solidification. Fe impurities were captured by primary SiC particles at the bottom of the ingot, which then segregated at the top of the ingot. When the pull-down rate was 5 μm/s, the solidification front was always close to the induction coil. Electromagnetic stirring produced forced convection that promoted Si+TiSi₂ eutectic alloy precipitation by mixing the melt and offsetting the temperature gradient caused by the precipitation of the primary phase, thereby inhibiting segregation. Thus, the optimal pull-down rate for fabricating Si+TiSi₂ eutectic alloy was 5 μm/s. At this pull-down rate, the maximum thickness of the Si+TiSi₂ eutectic alloy layer was 27 mm, and the removal rate of impurity Fe in this layer reached 98.98%.

Keywords: Si+TiSi2 eutectic alloy, electromagnetic directional solidification, segregation, metal impurity