Advancing near-infrared and blue hybrid laser welding: Energy efficiency and microstructural refinement in Al-Mg-Si dissimilar joints

Abstract

The integration of near-infrared (NIR) and blue laser welding technologies presents a promising approach to address the inherent challenges faced by traditional welding methods, particularly when applied to aluminum alloys. This study investigates the effects of NIR-blue hybrid laser welding on the microstructural evolution and mechanical properties of dissimilar Al-Mg-Si alloys welded joints, comparing different power configurations: 1700 W NIR, 1200 W NIR+ 500 W blue, and 1700 W NIR + 500 W blue. The results showed that the introduction of blue laser significantly improved energy absorption efficiency due to the higher absorption rate of aluminum alloys at blue laser wavelengths. The hybrid laser welding minimized keyhole-induced porosity by improving molten pool stability and reducing bubble entrapment. In addition, the appropriate hybrid laser power will improve the yield strength and ductility of the joints, which is attributed to the simultaneous enhancement of multiple strengthening mechanisms. The hybrid laser configuration promoted higher dislocation densities and refined precipitation phases, contributing to improved hardness, strength and ductility. The hybrid laser welding process, particularly the 1200NIR+ 500Blue joint, demonstrated an enhanced solidification rate, a higher nucleation site density, and a reduced grain nucleation radius, all of which facilitated the development of a finer grain structure due to the optimized energy input. However, excessive NIR laser power will weaken the grain-refining effect of the blue laser, leading to grain coarsening. The findings provide critical insights that contribute to the advancement of NIR-blue hybrid laser welding technologies for high-performance manufacturing applications.