Optimisation of process parameters and weld shape of high power Yb-fibre laser welded 2024-T3 aluminium alloy

A novel approach to welding crack sensitive 2024 aluminium alloy was made by using fibre laser. Bead on plate welding of 3 mm thick sheets of 2024-T3 was performed to determine the optimum sets of welding parameters including laser power, welding speed, power density and focal position, which meet the quality and specification requirements of aircraft structures. A correlation between these parameters and weld shape, microstructure, and defects was found. The weld quality was assessed in terms weld-seam geometry, root to width ratio, surface appearance, penetration depth, microstructure and defects. Microstructural analysis was performed using optical microscopy, scanning electron microscopy and energy dispersive spectroscopy. The parametric optimisation was conducted to obtain crack and porosity free full penetration welds with ideal sized face and root width or weld shape, and a minimal amount of undercut, underfill and reinforcement. While high-quality welds were produced, in some cases, micro-cracks less than 0.5 mm were observed in the weld metal as optimising the parameters only had a limited effect on completely shifting the crack sensitive composition. The addition of filler metal with a different chemistry was found to be also necessary to adjust the composition to a less crack sensitive range.