Droplet transfer in aluminum alloy laser-MIG hybrid welding coupled by high frequency pulses and its cladding characteristics

High frequency pulses (HFPs) power source were parallelly connected with the power source of single-pulse mode MIG arc, which are applied to laser-MIG hybrid welding. The cladding on A7N01 aluminum alloy was executed to investigate the dynamics of droplet transfer and arc with the effects of coupled HFPs through high speed camera observation. The shaping-characteristic and microstructure of cladding layer were also studied by metallographic analysis. The results show that the arc length and voltage increase after HFPs being coupled. The base current of single pulse MIG arc decreases, while the peak current has little changes compared with that without HFPs coupling. In conventional laser-MIG hybrid welding, the droplets are partly transferred as meso-spray mode. The finger-penetration weld can be obtained, which probably causing defects in the weld root. After HFPs being coupled, partly meso-spray transfer changes to completely spray transfer. The surface of cladding layer becomes smoother with the disappearance of fish-scale pattern and finger-penetration depth. Although the grain size has no significant changes, the size of second phase particles becomes smaller and more uniformly distributed in grains as strengthened phase.