Production of Fe–Ti Alloys from Mixed Slag Containing Titanium and Fe2O3 via Direct Electrochemical Reduction in Molten Calcium Chloride

Abstract

High-purity intermetallic β-Ti (FeTi4) and FeTi alloys were prepared via molten salt electrolysis from a titanium-containing waste slag and Fe2O3 mixture using molten CaCl2 salt as the electrolyte. The mixed slag powders were pressed into a pellet that served as a cathode, while a graphite rod served as an anode. The electrochemical process was conducted at 900 °C with a cell voltage of 3.1 V under an inert atmosphere. The formation process of the alloys and the influence of the Ti:Fe atomic ratio on the product were investigated. With an increased proportion of Ti, the phase of the product changed from FeTi/Fe2Ti to FeTi/FeTi4, and different structures were observed. At a Ti:Fe ratio of 1.2:1 in the raw slag, an alloy with a sponge-like morphology and a small amount of FeTi4 were obtained. During the initial stages of electrolysis, a large amount of intermediate product (CaTiO3) was formed, accompanied by an abrupt decrease in current and increase in particle size. The current then increased and Fe2Ti alloy was gradually formed. Finally, as the reaction process extended inside the pellet, the current remained stable and the product mainly contained FeTi and FeTi4 phases. The observed stages, i.e., CaTiO3(TiO2) → Fe2Ti(Ti) → FeTi(FeTi4), were consistent with the thermodynamic analysis.