The mechanism of in situ TiC/Al composite synthesis with XD method was studied by using DTA, X ray diffraction, TEM and optical microscopy. The results show that Al
3Ti phase forms firstly in aluminium matrix and then TiC phase is synthesized through the reaction between Al
3Ti phase and C powder. It is thought that Al acts as a catalyst during TiC formation, lowering activation energy and favoring the reaction.