Mechanical properties and microstructures of 6082-T6 joint welded by twin wire metal inert gas arc welding with the SiO2 flux

Twin wire MIG (metal inert gas arc welding) arc welding was employed on 6-mm thick 6082-T6 Al-alloy plate partially with SiO2 activating flux. The micro-structural characteristics of the weld joint were investigated using optical, scanning microscopy and energy dispersive spectroscopy. Mechanical properties were studied with micro-hardness and tensile test. Results show that no obvious difference from the microstructures of the joints prepared with and without SiO2 flux, the joint HAZ (heat affected zone) with SiO2 flux was observed to be slightly wider than the one without the flux. The weld joint penetration with SiO2 flux was about 26% deeper than what without SiO2 flux. The arc constriction and higher arc temperature were the main reasons for deeper penetration on twin wire MIG weld joint. The tensile test specimens prepared with and without the flux all showed plastic dimple fracture surfaces, SiO2 flux did not have any obvious effect on the micro-hardness and strength of the weld joint.