Effects of filler wire on microstructure and mechanical properties for fiber laser welding 6A02 aluminum alloy

6A02 aluminum alloy with 1.0 mm thickness was welded by fiber laser beam. And the ER4043 filler wire was also used during the welding course. The effects of filler wire on cross-section of welds and characteristics of joints (including microstructure, microhardness and tensile properties) were analyzed. The results show that the welded seam by laser welding with filler wire (LWFW) is very full. It also could increase the maximum assembly gap tolerance obviously. The microstructures of joint by LWFW, either the columnar structures near the fusion zone or the mixed microstructures (including columnar grains and equiaxed grains) in the weld center zone, are coarser than that by autogenous laser welding. The softening phenomenon of the former is more serious than that of the latter. The tensile strength in welded state of the former is basically equal to that of the latter, which could reach to 83.2% of the base metal level. However, the strength could be recovered by solution and ageing heat treatment, and higher than the base metal level. The joint elongation by LWFW is improved obviously and reaches to 21.29%, which is larger than 8.13% of that by autogenous laser welding.