In this research , Al-3%Vol.TiC nanocomposite was produced by accumulative roll bonding (ARB) technique after 10 cycles. These strips were joined by friction stir welding (FSW) in conventional (in-air) condition at the tool rotation rates 320 , 600 and 900 rpm and the travel speeds 100, 200 and 300 mm/mihy;. In additiohy;, the strips were welded in submerged (under water) condition to investigate the effect of the immersion method on the microstructure and mechanical properties of the joint . Transmission electron microscopy , scanning electron microscopy and image J analyses were used to evaluate the microstructure . A K type thermocouple was used for monitoring of temperature variation during FSW . Among the 9 welding parameters in the conventional condition, the highest tensile strength and hardness and lowest elongation were achieved in the joint obtained at 600rpm-300mm/min welding parameter (heat index 1200 mm -1 ) . Submerged friction stir welding under water results in lower peak temperature and because of lower heat input, final grain and subgrain sized in stir zone decreased . The hardness and tensile properties of submerged FS welded compare to the conventional FS welded improved. Fractography of FS welded sample showed ductile dimplehy;. The dimples were bigger in conventional condition as compared to that in submerged condition. Keywords: Nanocomposite , Accumulative roll bonding , Friction stir welding , Transmission electeron microscopy , Tensile strength
