In this thesis, Friction Stir Processing (FSP) was used to develop surface Al-Al 2 O 3 nanocomposite on Al2024 plate. A new procedure was introduced for applying the reinforcement particles in which 10 volume percent of Al 2 O 3 nanopowder, as the reinforcement, was added to the aluminum powder and milled for 1 hour. Composite powder was applied on Al2024 plate by atmosphere plasma spray and then the FSP was performed on the plate. In order to optimize the FSP parameters, microstructural and hardness evaluation were done. Optimized parameters including tool design, rotational speed, linear speed and tilt angle were determined to be 800 rpm, 25 mm/min and 3 0 respectively. Microstructural evaluation was performed by optical microscopy and Image Tool software. In order to examine the effects of the FSP process on hardness and wear behavior, hardness and wear tests were performed on base metal and FSPed samples. Dominating wear mechanisms were investigated by surface examination and studying of wear product using scanning electron microscopy (SEM). The thickness of nanocomposite layer produced by FSP was measured to be 600µm in which uniform distribution of Al 2 O 3 particles with good bonding with substrate were observed. Microstructural evaluation showed that FSP process significantly reduces the grain size in nugget zone, from 250µm (base metal) to 2.5µm. Maximum hardness of base metal, FSPed sample without Al 2 O 3 and FSPed nanocomposite were measured to be 90, 110 and 230 HV respectively. Wear test results showed improved wear resistance in FSPed and nanocomposite samples. Wear rate of base metal, FSPed sample and FSPed nanocomposite were 0.037, 0.027 and 0.004 mgr/m respectively