Suppressing porosity of a laser keyhole welded Al-6Mg alloy via beam oscillation

Oscillating laser beam was utilized to weld the Al-6Mg aluminum alloys. The porosity of the welds with different parameters were investigated. The higher values of oscillation frequency and oscillation amplitude were more effective for pore suppression. A wide range of oscillation frequency thresholds for different oscillation amplitudes that meet industrial porosity standards (below 1%) was found. The essential effect of this oscillation is to change the laser-induced keyhole velocity. There are more general rules when considering the keyhole velocity. An average keyhole velocity above 70 m/min completely inhibits the pores. The keyhole velocity threshold for pore suppression is nearly linearly correlated with the oscillation amplitude, for the keyhole velocity in the 30-70 m/min range. The lower porosity induced by oscillating laser beam improved the tensile strength of the lock butt weld, which was 36.3% higher than that of the weld without oscillation.