Study on laser-MIG hybrid welding characteristics of A7N01-T6 aluminum alloy

In this paper, an experimental study of laser-metal inert gas (MIG) hybrid welding of A7N01-T6 aluminum alloy in butt joint configuration was carried out. Visual examination and optical microscope were utilized to study the macro profile and microstructure, while mechanical properties of the welds were evaluated with the help of a tensile test and microhardness measurement. The joints were evaluated by the scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). Besides, X-ray microtomography was employed to characterize the morphology, quantity, and distribution of porosities in the weld seam. The results revealed that 4-mm thickness high-quality laser-arc hybrid welding butt joints were obtained with parameters of laser power 3.5 kW, welding speed 4 m/min, and welding current 140 A. The average tensile strength of welded joints reached 268 MPa, 76.6 % of that of the base metal. The loss was likely to be related to the presence of micropores, and further three-dimensional characterization indicated that there were altogether 4326 pores with diameters ranging from 0.1 to 79 μm in the tested sample, accounting for 0.57 % of the volume fraction and 4.56 % of the cross-sectional area fraction at the most. The existence of porosities, the dissolution, and coarsening of strengthening precipitates together promoted the joint softening in A7N01-T6 hybrid welding process.