Experimental investigations on mechanical properties of AA6061-T6 aluminum alloy joined by laser welding using digital image correlation

In industrial applications of laser welding of aluminum alloys, it is often a challenge to find optimal process parameters to produce welded joints of good quality. This study investigates the effect of changes in welding parameters on the resulting welding defects and tensile properties of laser-welded aluminum alloy joints. A high-power disk laser was used for welding 2.54 mm thick AA6061-T6 sheets with four different sets of process parameters. X-ray computed microtomography and full-field microhardness mapping were first used to characterize the as-welded joints. Surface strain mapping based on digital image correlation and a two-mirror optical setup was applied to tensile testing of welded joints up to ductile failure. It was found that the fusion zone of all four laser-welded joints has similar microhardness levels and spatial distributions. Small pores were detected in all four weld joints, except one had a few large pores. Both microstructural heterogeneities and surface geometric irregularities were found to induce highly non-uniform local tensile deformation in laser-welded joints. One set of laser welding parameters was identified to produce the aluminum welds with the best tensile properties even though its weld joint may contain a few relatively large pores.