Effect of Additional Element on Hybrid Laser Weldability in Al-Mn Alloys

Hybrid laser welding have been carried out, with bead-on-plate and butt welding setting, on Al-Mn and Al-Mn-Mg alloys, to evaluate the welding defects morphology. On bead-on-plate welding, keyhole mode was achieved without the welding defects at 60mm/s traveling speed with 2.12kW pulsed laser in Al-Mn alloy. The increase of maximum power of pulsed laser and Mg content caused a rise of welding defects, that is, porosities and cracks. Simultaneously, both penetration depth and bead width became larger, and aspect ratio of fusion zone (depth to width) also increased. X ray tomography clearly evaluated internal welding defects such as porosity. Morphology of fusion zone and welding defects were influenced by an incorrect root gap in butt welding. An increase in the root gap tended to reduce the porosity, and achieved higher aspect ratio of fusion zone, which was deeper penetration depth and wider bead width. On the other hand, underfill, as superficial welding defect, was clearly formed in both alloys. The root gap in butt welding was one of sensitive factors on the laser weldability besides Mg content and pulsed laser power.