An investigation of the reduction of TiO2 by Mg in H2 atmosphere

•The relative density of the precursor particles strongly affects the reduction kinetics.•Temperature affects the reduction kinetics and the residue O in the reduced powder.•The appearances of intermediates reflect the local availability of Mg reductant.•The morphology of the reduced product substantially inherits that of the original TiO2. Hydrogen assisted magnesiothermic reduction (HAMR) of TiO2 is a promising new process developed recently to produce Ti metal with low cost and less energy consumption. This work focuses on the understanding and optimization of the reduction process to control the quality of the reduced product. TiO2 precursor particles with different relative densities were prepared, and the effects of the relative densities on reduction by Mg in H2 were studied. The changes of oxygen contents vs. reduction time at various temperatures were investigated. The phase transformations during the reduction were analyzed both theoretically and experimentally. The relationship between the morphology of the reduced products and the relative densities of the TiO2 precursors was analyzed by SEM characterization and the likely reason for the morphology evolution was discussed.