Interface Behavior and Lap Shear Properties of the 7075-T6 Al FSLW Joint Using a Tip-Threaded Pin

摘要

For the purpose of reducing the hook and increasing the effective sheet thickness of the friction stir lap welding joint, a tip-threaded pin was used to weld 3?mm-thick 7075-T6 aluminum alloy in this work. Material flow behavior, joint formation mechanism and lap shear properties of the lap joints were mainly discussed. Results showed that when using the tip-threaded pin, lap joint with nearly aequilate stir zone (SZ) along thickness and rather flat hooks were obtained. When using high rotating speeds, the width of the lower SZ exceeded that of the middle SZ. A void, which resulted from the material loss near the lap interface, was observed at the same time. With increasing the rotating speed, the lap shear failure load of the joint initially increased and then decreased, while the fracture mode changed from tensile fracture to shear fracture mode. The maximum failure load of 17661?N was attained for the joint without void at 850?rpm.