Vacuum Electromagnetic Levitation Melting of Ti–Al Based Alloy Prepared by Aluminothermic Reduction of Acid Soluble Ti Bearing Slag

A Ti-Al based alloy was prepared by aluminothermic reduction of acid soluble titanium slag followed by electromagnetic levitation refining. It was observed from the XRD and microstructure analysis that the alloy after refining was mainly composed of TiAl₂ phase, with Mn and Fe dissolving into Al lattice, Ti₅Si₃, TiAl, and other metallic compounds. With increase of the vacuum degree or refining time, the phase of the alloy changed from an Al-rich compound to a Ti-rich phase due to Al loss by evaporation. The kinetics of Al evaporation demonstrated that the rate determining step of Al evaporation was controlled by the mass transfer in the liquid metal phase. The oxygen removal showed increasing tendency with increase of vacuum degree and refining time. The removal rate of oxygen after refining at 1858 K, 400 Pa for 25 min was over 40% and the final percentage of oxygen in the alloy was 0.59 wt%. Vickers hardness of the alloy showed increasing tendency with increase of vacuum degree and refining time, while its bending strength showed decreasing tendency. These results are mainly attributed to the comprehensive effect of oxide inclusions removal and phase transition in the refining process.