Overlap laser welding of 5052-H36 aluminum alloy: experimental investigation of process parameters and mechanical designs

Abstract In this study, the laser welding process is used to join 1.6-mm-thick AA5052-H36 sheets in an overlap joint configuration. Both pulse and oscillation laser beam welding were investigated for the first laser pass. Oscillation beam laser welding in continuous-wave mode show more stable and sound weld with no porosity defects compare to pulse wave (PW) mode. The adopted welding power, speed, frequency, and defocus are 8 kW, 6.5 m/min, 150 Hz, and + 8 mm, respectively. The obtained stitch welds are defects free (blowholes, micro-cracks, or porosities). A circular oscillation ramp-up/ramp-down PW mode is adopted for a second laser surface re-melting (LSR) pass. The corresponding welding power, speed, frequency, and defocus are 5 kW, 2.5 m/min, 500 Hz, and + 15 mm, respectively. Shear tests are then performed to evaluate the mechanical properties of single lap joints (SLJ) for different stitch weld shapes, 2 gap tolerances (0 and 0.5 mm), as well as with/without LSR pass. The best tests’ reproducibility and highest dissipated energies (~ + 42% when compared to the perpendicular direction) are obtained when the stitch weld direction corresponds to the loading direction. The second LSR pass provides more aesthetic joints with higher shear resistance (~ + 1% to + 3%) due to a decrease in the weld surface underfill and undercut imperfections of the stitch weld. The part-to-part gap leads to higher shear resistance (~ + 20%) owing to 2 main reasons: larger welding surfaces at the joint interface and higher hardness of the fusion zone. These findings are of great value for including laser welding technology in the automotive and surface transportation industries. Graphic abstract