Microstructure and alloy element distribution near the fusion line of aluminum alloy 6061 in laser wire-filling welding

Aluminum alloy 6061(AA6061) sheets of 4 mm in thickness are joined by laser wirefilling welding (LWFW) using the ER4047 welding wire. Microstructure and alloy element distributions near the fusion line are characterized and are investigated by optical microscope, scanning electron microscope, energy dispersive spectrometer. The results showed that the well-formed welded joints are obtained with a few thermal cracks near the fusion line. The coarse grain and a reduction in the weight ratio of magnesium to silicon can be observed, when the welding speed decreases under constant laser power. The thermal crack is caused by the decrease of the weight fraction of magnesium and the proportion of silicon content has an effect on the microhardness of welded joints. By properly controlling the welding speed, the various properties of AA6061 LWFW joints can be balanced.