The combustion synthesis of $Al_2O_3-TiC-Ti$ composite by self-propagating reaction from a powder mixture of $TiO_2,$ Al, and C was investigated. The combustion wave quenching technique which can freeze the combustion wave front was used to analyze the intermediate phase formed during the combustion reaction. The reaction was composed of the aluminothermic reduction of $TiO_2$ and the reaction of $TiC$ formation which were occured in series. The aluminothermic reduction of $TiO_2$ was preferentially initiated at about 1000℃ with aid of the melting of Al and the capillary spreading of Al melt between $TiO_2$ particles. It was passed through the intermediate phases of oxygen- deficient titanium oxides and the liquid solution made of Ti, Al, and O. And $Al_2O_3$ grains were formed and grew in the liquid phase so that a composition of liquid phase was continuously altered from the Al-rich to the Ti-rich to be finally in the solubilty limit of Al in Ti melt. The aluminothermic reduction of $TiO_2$ finally produced $Al_2O_3$ and Ti-rich phase. The reaction of TiC formation was the last stage and started at about the melting point of Ti. The formation of three-dimensionally interconnected $Al_2O_3$ structure which was typical in the combustion synthesis of $TiO_2-Al-C$ system was mainly due to the high combustion temperature which was come from the reaction between Ti and C in the latest stage of the combustion reaction. The decrease of the combustion temperature by the addition of TiC diluent and the decrease of the content of C in the reactant could change the structure of $Al_2O_3$ skeleton from the interconnected one to the isolated one. This isolated structure showed the superior densification behaviour than the interconnected one when the as-synthesized product was hot-pressed at the temperature of 1460℃. Therefore, it could be concluded that the microstructural control of the combustion-synthesized product was possilble by the control of the adiabatic temperature in $Al_2O_3-TiC-Ti$ composites and was the important factor in the SHS densification.
