Abstract: Friction stir lap welding was performed on 6061-T6 and 2024-T4 aluminum alloy plates with dimensions of 200mm×90mm×2.5mm and 200mm×90mm×2.8mm,respectively,at a fixed welding speed of 100mm/min and adjustable stirrer speed of 400r/min,600r/min and 800r/min.The results showed that the weld surface was smoothest when the speed was 600r/min;With the increase in stirrer speed,it can be seen that the degree of mixing of 6061 and 2024 aluminum alloy at the interface increased significantly;compared with the base material,the weld nucleus area grain is small and uniformly distributed,the lower part of the weld nucleus area than the upper part of the grain is finer,presumably related to the lower part of the weld nucleus material is more strongly stirred;with the increase in stirrer speed,the joint failure load first increases and then decreases,When the speed is 600r/min,the failure load reaches the maximum value;the stirrer torque and axial force decrease with the increase of speed.