Enhanced mechanical properties and penetration in AA 6061-T6 welds using flux bounded TIG (FBTIG) welding

Flux bounded tungsten inert gas (FBTIG) welding is investigated as an advanced joining technique to overcome the limited penetration and joint efficiency of regular tungsten inert gas (TIG) welding in AA6061-T6 aluminum alloy. Bead-on-plate welding of 8 mm thick plates showed a significant increase in effective weld zone depth from 1.6 mm in regular TIG weld to 5.2 mm in FBTIG weld. Tensile test results revealed that regular TIG welds could achieve only 42% of base metal strength with ultimate tensile strength (UTS) of 129 MPa and elongation of 6.5%, whereas FBTIG welds showed improved joint efficiency of 54% with UTS of 166 MPa and elongation of 8.5%. Post-weld heat treatment further increased strength and ductility, achieving 65% joint efficiency with UTS of 200 MPa and elongation of 10%. Scanning electron microscope fractography confirmed progressive grain refinement from TIG to FBTIG welds, with finer and more uniform dimples indicating enhanced ductile fracture behavior. Post-FBTIG weld heat treatment showed increased equiaxed and relatively coarse fracture surface features, suggesting changes in stress and precipitation conditions that favor enhanced void development and recovery of ductility demonstrating the novelty of FBTIG welding process.