Influence of BA4047 filler addition through Mamdani fuzzy logic optimization for double-sided T-joint welding of aluminum alloys using low-power fiber laser

Double-sided laser beam welding of skin-stringer joints is a proven method for many industrial applications such as in aircraft assemblies where riveted differential joints are being replaced with welded integral structures. In the present study, dissimilar aluminum alloys of AA2024-0 and AA7075-T6 were laser welded on both sides in a T-joint configuration using a low-power Yb-fiber laser with the addition of a BA4047 filler wire. The optimized parameters were determined by developing a Mamdani fuzzy smart model. The influence of BA4047 filler wires on weld morphology was investigated using optical microscopy (OM) and scanning electron microscope (SEM). The cross-section of the joints revealed that the fusion zone (FZ) and heat affected zones (HAZ) are wider when filler wire was added as compared to those without it. This result shows that the low-power fiber laser has sufficient energy to melt the tip of the filler wire and subsequently the base materials, forming a liquid bridge to facilitate the smooth flow of molten metal between the stringer and the skin. No obvious voids were observed in the cross-sections of the joint interface. The strengths of joints were evaluated using a pull test, and hardness values were measured at the base metal (BM), FZ, and HAZ using the Vickers hardness test. At lower welding speeds with constant low-laser power, it was shown that the addition of the aluminum-silicon base alloy has increased the overall hardness and welding strengths of the samples.