Dual-beam laser welding of ultra-thin AA 5052-H19 aluminum

Welding of 0.05 mm (0.002 inch) thin AA 5052-H19 aluminum samples in lap-joint configuration was conducted autogenously (no filler metal) using dual lasers that included Nd:YAG and diode with a zero inter-beam spacing. The 70-ns pulsed Nd:YAG (1064 nm) laser acted as the welding tool while the continuous wave diode (810 nm) laser with interaction times of 40-120 ms served to improve the light absorption characteristics of aluminum through preheating and oxidation effects. The microstructure, composition, flaws, and hardness of the joint were evaluated by scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, and micro-indentation hardness test. The dual-beam welding technique was also compared with single-beam (Nd:YAG) welding. Results of parametric effects are displayed in the form of processing maps. Deeper penetration, better weld quality (less humping and cutting), and increased hardness were observed in dual-beam welds when compared with single-beam welds. The most astounding result was a nearly 200% increase in hardness over the base metal in dual-beam welding. This can be explained by the oxygen pickup in a dual-beam weld due to longer heating and amorphous microstructure of aluminum oxide as revealed by energy dispersive X-ray spectrum and X-ray diffraction respectively.