In the present study Ti5Si3-Al2O3 nanocomposite was synthesized by a displacement reaction between Al and TiO2 in ball milling of TiO2, Al and Si powders. The effect of milling time and heat treatment temperatures were also investigated. The structural changes of powder particles during mechanical alloying were investigated by X-ray diffraction (XRD). Morphology and microstructure of powders were characterized by scanning electron microscopy (SEM). It was found that after 10 h of MA, the reaction between Al and TiO2 initiated in a gradual mode and after about 45 h of milling, the reaction was successfully completed. The final product consisted of Ti5Si3 intermetallic compound with a crystallite size of 13 nm and amorphous Al2O3. Heat treatment of this structure at 1050 degrees C led to the crystallization of Al2O3 and ordering of Ti5Si3. The crystallite size of Ti5Si3 and Al2O3 after annealing at 1050 degrees C for 1 h remained in nanometer scale. So the final product appeared to be stable upon annealing. (C) 2011 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.