Abstract: 6 mm thick 15vol.% SiCp/2009Al matrix composite rolled plates were subjected to T-type friction stir welding (FSW) under the rotation rates of 800−1 200 r/min and welding speeds of 100−150 mm/min. The results show that, defect-free joints were obtained and the SiC particles were broken up during FSW; The crushing degree of SiC particles increased with enhancing the welding speed and decreased with the increase of the welding speed. The micron-level precipitates in the nugget zone (NZ) were broken up and dissolved, and then reprecipitated along the fine grain interface of NZ. There are two low hardness zones (LHZ) at both advancing and retreating sides of the horizontal plate of T-type joint, and the hardness of the LHZ close to the NZ is lower than that of the LHZ far away from the NZ. Under the constant welding speed of 100 mm/min, the tensile strength of the T-type joint was unchanged when increasing the rotation rate from 800 r/min to 1 200 r/min. Under the constant rotation rate of 800 r/min, the tensile strength of the joint increased as increasing the welding speed from 100 mm/min to 150 mm/min. The T-type joints fractured at the junction of horizontal and vertical pates during tension test.