Effect of heat input on macro morphology and porosity of laser-MIG hybrid welded joint for 5A06 aluminum alloy

The 5A06 aluminum alloy butt joint is fabricated by laser-metal inert gas (MIG) hybrid welding in this investigation. The macro morphology and porosity of welded joints under different heat input are observed by optical microscope. The effect of the laser, MIG, and hybrid heat input on macro morphology and porosity of welded joint is investigated. Furthermore, the force condition inside the laser-MIG hybrid welding pool is analyzed to explain the influence mechanism of heat input on macro morphology and porosity in theory. It is found that the cross-section area of weld seam (WS) is increased with the welding heat input. The porosity of the full-penetration WS is smaller than the partial-penetration WS owing to the different flow characteristic of molten pool. The higher MIG heat input is beneficial to reduce the porosity. It is illustrated that the welded joint with a lower porosity is expected to be obtained under the energy ratio coefficient of 0.5.