Study on stability and microstructure properties of oscillating laser welded 5A06 alloy with narrow gap

•The oscillating laser with a cycloid scan path could restrain the formation of pore defects in aluminum alloy laser filler welding.•The increase in oscillating amplitude and frequency could inhibit the formation of pore defects.•The stirring effect on the molten pool of the oscillating beam made the droplet enter the pool instead of making a spatter.•The oscillating laser avoided the plasma in the groove to a certain extent and increased the energy on the base metal.•The defect-free multilayer welding seam of 18 mm thick was realized by oscillating laser with a cycloid path. In order to reduce porosity and improve welding quality during laser welding with narrow gap of 5A06 aluminum alloy, a laser oscillation method was applied in this study. By comparing the welds with different scan paths, it was found that the laser oscillation with cycloid path could restrain the formation of pore defects, improve the surface appearance, and enhance the stability of the molten pool. EBSD results under different scanning paths described the effect of laser oscillation on the microstructure of the weld. The influence of oscillation amplitude and frequency on welding quality was studied as well. The pore defect could be eliminated when the amplitude was greater than 2 mm and the frequency was greater than 150 Hz. Dynamic information of the molten pool and plasma was obtained through a high-speed camera system. It was found that the oscillating laser could partly avoid the influence of the plasma on laser energy attenuation. Finally, a multi-layer welding experiment was carried out using the optimized oscillated laser parameters.