Improving the performance of adjustable-ring-mode laser butt weld by double-pass welding configuration

This paper evaluates the successive double-pass laser welding using an adjustable-ring-mode beam for dissimilar AA5754-AA6005 butt welds, benchmarked against single-pass welding. The effects of core-to-ring power ratios and welding configurations on weld geometry, microstructure, porosity formation and mechanical performance are investigated. I n single-pass welding, reducing power ratio leads to less weld concavity, grain refinement in the fusion zone, and less porosity. The weld strength increases from 75.7% to 86.6% of AA5754, the weaker base material, when the laser beam shifts from the core-only mode to the core-to-ring power ratio of 0.33. By contrast, double-pass welding, using lower laser power per pass, can produce a shallower fusion zone and a more symmetrical weld profile with reduced weld concavity. Re-melting and re-solidification in the overlap region between two passes is beneficial for reducing weld porosity and disrupting the solidified microstructure, leading to overall grain refinement. The highest joint efficiency is achieved in the double-pass weld with the lowest power ratio of 0.55, reaching 93.5% of AA5754. A more tortuous crack path that deviates in the overlap region and then advances along the second-pass fusion boundary further contribute to the superior strength. These findings highlight the potential of double-pass laser welding as a viable technique for achieving high-quality aluminium welds, particularly for applications where mechanical integrity and dimensional tolerance are critical.