Influence of rotating speed on microstructure and peel strength of friction spot welded 2024-T4 aluminum alloy

In the present study, friction spot welding (FSpW) process was used to weld alclad 2024-T4 aluminum alloy. Influence of tool rotating speed on microstructure and peel strength of the FSpW joints was mainly discussed. Results show that inner defects such as voids and incomplete refilling can be observed at the thermal-mechanically affected zone/stir zone (TMAZ/SZ) interface. Microstructures of the pin affected zone (PAZ) and sleeve affected zone (SAZ) show much difference due to different material flow behaviors. With increasing the rotating speed from 900 to 2100 rpm, microhardness of the SZ decreases, and peel strength of the joint firstly increases and then decreases. Maximum peel failure load of 950.9 N is attained when using 1300 rpm. Joints fracture at the TMAZ/SZ interface when using small rotating speed and fracture at TMAZ when heat input is increased.