Weld zone porosity elimination process in remote laser welding of AA5182-O aluminum alloy lap-joints

A laser beam with a travelling speed of 43.5 m/min along circular oscillation paths was utilized to weld AA5182-O aluminum alloys in a lap joint configuration for automotive application. Experimental results showed that the porosities formation in the weld zone can be dramatically reduced compared with the case following the straight welding path and the welding speed of 3.0 m/min. The porosity-free welds were achieved and the corresponding tensile shear strength was significantly enhanced. The relationship between overall area percentage of the porosity in the weld zone and the circular oscillation parameters, which include amplitude A and period length L, was investigated. It was found that a combination of A and L with the value of A larger than the laser beam focal diameter was crucial for eliminating the porosity in the weld zone. A welding mode that combines the keyhole mode with conduction mode was proposed to explain the porosity elimination mechanism. A designated experiment was conducted to validate the hypothesis.