Surface cracks repair in AA6061-T6 aluminum alloys using friction stir processing

Friction Stir Welding (FSW) is an advanced solid-state joining technique that offers an effective solution for repairing surface cracks in aluminum alloys. This study investigates the repair of an artificially induced 2 mm square groove in AA6061-T6 aluminum alloy plate; resemble pre-repair preparation, using friction stir processing (FSP), incorporating an aluminum filler rod and silicon carbide (SiC) nanoparticles as a reinforcement to ensure complete crack sealing. FSP was conducted on both cracked and crack-free samples, with a focus on the impact of tool offset during the repair process. Tool offsets of 0 mm, 1.75 mm, and 3.5 mm were employed toward the advancing side to assess their influence on the repair process. Mechanical testing, microstructural characterization, temperature, and force analysis were performed to comprehensively evaluate the repair strategy. The repaired samples exhibited an average ultimate tensile strength (UTS) of approximately 180 MPa, closely matching the 186 MPa observed in crack-free bead-on-plate welds. Additionally, the microhardness at stir zone (SZ) improved to average values of 77 HV for 0 mm offset and 80 HV for 1.75 mm offset, compared to 70 HV in the bead-on-plate welds. Despite the presence of microstructural defects, the use of tool offset contributed to satisfactory mechanical performance. However, samples welded with 0 mm tool offset exhibited slightly superior mechanical properties. Overall, this research highlights the feasibility of using FSP, combined with SiC nanoparticles reinforced filler material and tool offset control, as a promising approach for effective surface crack repair in aluminum alloys, providing a foundation for further process optimization and industrial application.