Controlling solidification cracks in laser beam welding of AA6005 using Al2O3 and TiC nanoparticles dispersed in a Cu coating

Laser beam welding is a critical joining method for wrought 6xxx series aluminium (Al) alloys; however, its broader adoption is hindered by the susceptibility to solidification cracking, which undermines weld integrity and restricts the production of high-quality joints. To mitigate cracking susceptibility, this study explores a novel approach involving the use of alumina (Al₂O₃) and titanium carbide (TiC) nanoparticles introduced into the fusion zone of laser welded AA6005 aluminium sheets via electrophoretic deposition (CuSO₄ bath, ∼40 nm nanoparticles, varying concentrations/times). Microstructural analysis revealed that the incorporation of both Al₂O₃ and TiC nanoparticles on AA6005 led to an overall 65% grain refinement, effectively preventing centreline cracking during welding. Lap shear testing demonstrated a significant improvement in joint strength, with a 10% increase for Al₂O₃ coated samples and a 13% increase for TiC coated welds compared to the uncoated material. Notably, TiC outperformed Al₂O₃ at higher concentrations, exhibiting more uniform dispersion with reduced agglomeration and porosity. In contrast, Al₂O₃ showed a tendency toward particle clustering and pore formation at elevated concentrations, which limited its strengthening efficiency. This highlights the potential of nanoparticle reinforcement for enhancing the reliability and performance of laser welded 6xxx aluminium alloys.