Effects of the laser spot size and beam wobbling on the properties of aluminum 6061 weld metal

The effects of the spot size and beam wobbling on the mechanical properties and microstructure of the AA 6061 aluminum alloy during laser welding have been investigated. Changing the spot size from 0.6 to 0.3 mm reduced the required heat input for full penetration by 56% for a static laser beam and by 62% for a wobbling laser beam. Using a 0.3 mm diameter spot with beam wobbling reduced the severity of surface defects such as undercuts and excessive reinforcement. When the heat input and bead width were increased, laser beam wobbling increased the width of the equiaxed microstructure region in the weld metal. Grain refinement and the reduction in solute strengthening due to evaporation only had small effects on the weld metal strength.