A novel technique for repairing Keyhole in the aircraft assembly technology employing friction stir additive manufacturing

Abstract

Recently “Friction Stir Welding“ (FSW) has been one of the significant inventions in the welding and manufacturing world. But in FSW or any friction stir techniques, appearing “Keyholes” became a common issue. The retraction of non-consumable rotational pin tools mainly causes the “Keyhole.“ This research illustrates a novel approach called “Friction Stir Additive Manufacturing” (FSAM) is used to repair the “Keyhole.“ The hole was successfully repaired by using a series of pin-less rotational tools. In this research, aluminum alloy 7N01 was chosen as the “Base Material” (BM), and the “Keyhole“ in this alloy was investigated. Many microstructural properties of the joint were observed. Microstructures of the joint, especially the in the “Filling Zone” FZ, were observed. The result shows that it was repaired successfully without any defect appearing in the FZ of the joint employing the transverse velocity of 2 mm/min and “Rotational Speed” (RS) of 1600 rpm. The FZs are analyzed by equiaxed grains. At the transverse velocity of 2 mm/min and the RS of 1600 rpm, the “Tensile Strength” and “Elongation” of the joint reach the maximum values of 311.5 MPa and 7.6 %, which indicate up to 82.2 % and 96 % of defect-free FSW joint, respectively. In addition, the fracture surface morphology shows various dimples, indicating good mechanical properties with typical ductile fracture.