Self-propagating reaction mechanism of Mg–TiO₂ system in preparation process of titanium powder by multi-stage reduction

The novel method for the preparation of titanium powder by multi-stage reduction was proposed. The primary reduction adopted self-propagating high-temperature synthesis (SHS) mode. This paper focuses on the primary reduction process of Mg–TiO₂ system under the condition of off-balance reaction. The effects of different material ratios, material arrangement methods and reaction initiation modes on the SHS reaction process of Mg–TiO₂ system and its reaction mechanism were systematically studied. SHS mode was used to Mg–TiO₂ system, and non-stoichiometric low-valent titanium oxide intermediate including α-Ti (Ti₂O type) and TiO was directly obtained (with oxygen content of 13.93 wt%). SHS reaction initiated by local ignition is more sufficient than by overall heating method. Compared with the loose setting materials, the compacts can increase the effective contact interface of the reactants, and SHS reaction proceeds more sufficiently, which is favorable for obtaining lower oxygen content product. The adiabatic temperatures of the Mg–TiO₂ system at different initial conditions were calculated according to the improved calculation method. When the initial temperature is 298 K, the adiabatic temperature of Mg–TiO₂ system is between 1363 and 2067 K at different material ratios. Therefore, unreacted or partially excess Mg at the reaction front will diffuse into the unreacted region in gas or liquid form, thereby preheating the material and initiating further SHS reaction.