Performance enhancement of aluminum infrared laser welding by preconditioning with nanosecond laser pulses

We condition the welding zone of the aluminum surface with nanosecond laser pulses prior to welding with infrared laser radiation to increase the process efficiency and weld quality. The high reflectivity of aluminum for infrared laser radiation (95% at 1064 nm) leads to poor process efficiency of aluminum laser welding processes. To increase the workpiece's absorptivity, the welding zone is conditioned with nanosecond laser pulses at a wavelength of 532 nm. The samples are nonalloy, 0.5 mm thick aluminum, and 1.5 mm thick Al5356 alloy. Welding is performed with a continuous Nd: yttrium aluminum garnet (YAG) laser with an output power of 2 kW, a pulsed Nd:YAG laser with an average power of up to 90 W, and a pulsed Nd:YAG laser with an average power of up to 20 W. Through preconditioning with nanosecond laser pulses, full penetration welding is achieved with an increased welding speed. At the same welding speed, the bead size of the weld increases and deeper penetration of bead on plate welding is obtained. The authors observe higher surface oxygen content of the preconditioned aluminum surface which is expected to increase the absorptivity. Pore formation is reduced when employing the preconditioning on the Al5356 alloy.