Relationship between pool characteristic and weld porosity in laser arc hybrid welding of AA6082 aluminum alloy

Effects of welding parameters on the porosity of laser arc hybrid welded AA6082 aluminum alloy were investigated. The percent porosity was examined by X-ray non-destructive testing. The pool shapes were characterized by weld transverse and longitudinal profiles, which were observed by optical and scanning electron microscopes with elemental tracer technique, respectively. Under optimized welding parameters, the weld porosity could be reduced to less than 0.5%. It was found that the pool shape characteristics were closely relative to weld porosity. A volume characteristic coefficient, Φ was then proposed by pool profiles to predict the percent porosity of hybrid welds. The higher the Φ, the easier the bubble escaping away the pool, and the lower the weld percent porosity. When the Φ was larger than 0.52, the weld percent porosity was less than 0.5%, which is the criterion of first grade weld.