In the present study, Al-5Vol.%SiC composite was manufactured by accumulative roll bonding (ARB) process after 10 cycles. Subsequently, the composite plates were joined using friction stir welding (FSW) at the tool rotation speeds of 900, 1120 and 1400 rpm and the welding speeds of 63, 80 and 100 mm/min. In addition, using 4 pin geometries (cylindrical, triangular, square and hexagonal), the effect of pin profiles on mechanical properties of joints were investigated. Microstructural evolutions in the Stir Zone (SZ) of the welded samples were investigated by Scanning Electron Microscopy (SEM). A K type thermocouple was used for monitoring of temperature variation during FSW. After 10 ARB cycles, the composite microstructure showed that the reinforcement particles were distributed uniformly in the Al matrix without porosities in the Al-Al and Al-SiC interfaces. Hardness and tensile strength of produced composite were 2.26 and 2.5 times as high as that of the annealed pure Aluminum, respectively. Whereas, the elongation of the composite was drastically decreased by 22% in comparison to that of the annealed pure Al. SEM observation of fracture surfaces showed that the rupture mode in the composite was ductile rupture type. The composite was not joined at 900rpm-100 mm/min welding parameter. In addition, voids were found in SZ of welds using welding speeds of 63 and 80 mm/min at 900rpm. The voids drastically decreased the tensile strength of joints obtained at the parameters. Using greater rotation speed, sufficient heat input was provided for material flow during FSW and desirable joints were obtained. Among the other welding parameters, the most tensile strength and hardness and the lowest elongation were achieved in the joint obtained at 1120rpm-100mm/min welding parameter (revolution pitch of 0.089mm/r). In contrary, the least tensile strength and hardness and the most elongation were achieved in the joint obtained at 1400rpm-80mm/min (revolution pitch of 0.057mm/r). Fractography of the tensile fracture surfaces of FS welded samples revealed ductile dimples which were grown and deeper at less revolution pitches. The microstructure and mechanical properties of the FS welded composite was significantly affected by the tool pin profile. The microstructural evaluation of stir zones showed that the most fragmentation and distribution of SiC particles were obtained by square pin. The greatest hardness, tensile strength and elongation were achieved in the joint obtained by square pin. Hexagonal pin caused deep voids in SZ by which the tensile properties drastically decreased. Keywords: Aluminum, Accumulative roll bonding, Friction stir welding, Revolution pitch, Heat input, Tensile strength
