What role does magnesium play in the Kroll process?

In the Kroll process, magnesium (Mg) serves as the reducing agent used to convert titanium tetrachloride (${\text{TiCl}}_4$) into metallic titanium.12

The reaction occurs within a sealed steel vessel at temperatures ranging from 800 to 1,000 °C (1,450 to 1,800 °F) under an inert argon atmosphere to prevent contamination. During this process, magnesium reacts with the titanium tetrachloride to produce titanium in the form of a highly porous material known as sponge, along with magnesium chloride (${\text{MgCl}}_2$) as a byproduct. Following the reaction, the magnesium chloride is typically separated from the titanium sponge and recycled through electrolytic cells to recover magnesium for future use in the reduction process.1