Comparative study of hybrid laser-MIG leading configuration on porosity in aluminum alloy bead-on-plate welding

Laser-metal inert gas (MIG) welding is a promising welding technology, which presents many attractive properties. However, porosity still remains a serious problem in laser-MIG welding of aluminum. In this experimental study, the effect of leading configuration on porosity formation and distribution in laser-MIG bead-on-plate welding of A7N01 alloy was investigated. Experiments on arc current, welding speed, and arc configuration were performed comparatively for two leading configurations, respectively. The welds were analyzed with X-ray photographs and cross-section observations. Pores in laser-MIG-welded samples were mainly keyhole-induced. The concept of porosity area fraction was used to evaluate the severity of pore defect. The maximum porosity area fraction presented at different arc currents in the two leading configurations (in laser leading welding, it is 150 A, while in arc leading welding, it is 110 A). With welding speed increasing, porosity area fraction decreased. Bubble escape condition was deduced and used to discuss the probable mechanism of the effect of leading configuration on pore formation. The results showed that leading configuration was considerable in porosity minimization and prevention.