An Investigation on the Mechanism of TiC+Al₂O₃ Formation in the Combustion Synthesis of the Mechanically Activated TiO₂-Al-C System

A mechanism for the combustion synthesis of TiC+Al2O3 was proposed in a mechanically activated TiO2-Al-C system. As-milled powder mixture was analyzed using XRD and TEM techniques where no chemical reaction and/or inter-particle diffusion were identified. The results obtained from DTA tests on unmilled powder revealed that the combustion synthesis occurred in a single step at 962 ºC while the synthesis of mechanically activated powder mixture occurred in three different stages. The XRD analysis on the synthesized samples of 8 hour premilled powder at different temperatures showed that the three stages were as follows: First the reaction between Al and TiO2 takes place forming Al3Ti, Ti2O3, and Al2O3 at 700 ºC. In the second step, Ti-rich titanium aluminides (AlTi, AlTi2, and AlTi3) and TiO, are formed at 923 ºC, and finally the formation of TiC+Al2O3 is completed at 1329 ºC.