Oscillating laser beam welding of additively manufactured Al-Cu with hot-rolled Al-Mg dissimilar aluminum alloys: The role of laser beam offset

Wire arc additive manufacturing (WAAM) of TiC particle-reinforced Al-Cu alloy shows great potential for rapid manufacturing of large-scale lightweight aerospace structures, which often require subsequent joining with conventionally processed alloys. However, when WAAM-fabricated Al-Cu is joined to hot-rolled Al-Mg alloy, severe porosity defects and limited joint performance remain challenging issues. To address these challenges, this study investigates oscillating laser beam welding of WAAM-fabricated TiC_p/Al-Cu alloy and hot-rolled Al-Mg dissimilar alloys. Effects of laser beam offset on weld defects, microstructural evolution, and mechanical properties of additively-manufactured Al-Cu with hot-rolled Al-Mg dissimilar aluminum alloy joints are aimed to be elucidated. The results indicate that a 0.5 mm laser beam offset towards the Al-Cu side refines the weld grain structure but increases porosity and expands the heat-affected zone softening region. In contrast, offsetting laser beam 0.5 mm towards Al-Mg side effectively suppresses porosity defects and reduces softening, resulting in optimal mechanical properties with an ultimate tensile strength of 300 MPa and elongation of 6.2 %. Laser beam offset effectively adjusts the fusion ratio, thereby regulating the distribution of alloying elements, hydrogen content, and inoculant particles within the weld seam. This approach offers novel insights into overcoming critical challenges in dissimilar aluminum alloy welding, particularly under varying base metal processing methods.