Experiment and prediction of weld morphology for laser oscillating welding of AA6061 aluminium alloy

Effects of oscillating diameter ( D) and frequency ( f) on weld surface and cross-sectional morphologies were investigated in laser welding of AA6061 aluminium alloy with circular beam oscillation. Weld surface was mainly characterised by straight line shape when f > 10 Hz. Weld cross-section transformed from slender nail to irregular shape, dumpy nail, rectangle and crescent shape in sequence with the increase of D and f. A modified model considering material thermal properties was developed to predict the surface feature, especially whether the weld totally overlapped or not. A new normalised enthalpy was proposed to predict the keyhole mode of laser oscillating welding by considering materials thermal properties and remelting effect, which was suitable to explain the formation of cross-sectional morphology.