AA7075 bit for repairing AA2219 keyhole by filling friction stir welding

In the present study, 7.8 mm thick AA2219 rolled plates were successfully filling friction stir welded (FFSW) without keyhole using a semi-consumable tool. The influences of the bit's geometric parameters and the plunge speed on the joint's mechanical properties were investigated. Microstructure of the joint, especially at the interface, was observed. The results revealed that the AA7075 bit's employment was able to decrease the shedding bit material effectively. During tensile tests, the maximum ultimate tensile strength (UTS) and elongation of the joint were 179.6 MPa and 13.7%, equivalent to 96.6% and 99% of the original defect-free friction stir welding (FSW) joint, respectively. The defect-free FFSW joints were produced at lower plunge speeds, and the fracture locations were at the softened region within the heat affected zone (HAZ) adjacent to the thermo-mechanically affected zone (TMAZ) on the retreating side. With increasing the plunge speed, the fracture location was more mainly dependent on the interface strength instead of the hardness distribution.