Why is magnesium used to reduce titanium tetrachloride in the Kroll process?

In the Kroll process, magnesium is used as a reducing agent to convert titanium tetrachloride (TiCl₄) into metallic titanium.12

The preparation of pure titanium is challenging because the metal is highly reactive toward oxygen and nitrogen at elevated temperatures, and it readily forms stable carbides if reduced with carbon. To overcome these difficulties, the Kroll process employs molten magnesium to strip the chlorine from TiCl₄ in a sealed, inert argon atmosphere at temperatures between 800 and 1,000 °C.31

This reaction produces titanium in the form of a porous "sponge," with magnesium chloride (MgCl₂) entrapped in the pores. The resulting salts can be separated from the metal and recycled through electrolytic cells to recover magnesium for reuse in the reduction process.1