Numerical investigation of pulsed welding on aluminum alloy with a dual-region laser source: Exploring non-equal pulse parameters

Laser welding is a widely employed technique in modern industry, valued for its ability to achieve high-speed and high-quality welds. However, the weld quality depends heavily on precise control of laser parameters, as improper settings can lead to common defects. For aluminium alloys, such as 6082, minimizing heat input and managing cooling rates are critical to prevent issues like solidification cracking and ensure consistent weld integrity. Pulsed laser sources, as opposed to continuous ones, offer the advantage of reducing thermal stresses while maintaining high penetration depths. This study numerically investigates a dual-region laser source operating in pulsed mode for micro-welding applications. The laser comprises a high-intensity core for deep keyhole formation and an outer ring designed to stabilize the molten pool. Using a Volume of Fluid-based simulation framework, various pulse strategies were evaluated and compared to a novel configuration where the core operates in pulsed mode while the ring remains continuous. The results show that traditional rectangular pulses produce the highest cooling rates, increasing the risk of solidification cracks. However, incorporating a cooling-down phase and ramping the pulse shape effectively reduces the cooling rate, resulting also in more homogeneous penetration depths. The constant base power from the outer ring further enhances this effect by preheating the material before the pulse and extending the solidification time afterward. This extended solidification time reduces cracking risk and improves surface roughness. The study concludes that controlling the pulse shape and utilizing a constant base power from the ring can significantly reduce the cooling rate—by up to 45%, depending on the pulse shape—thereby enabling high-speed, high-quality welding of aluminium alloys, which are traditionally difficult to weld due to their thermal sensitivity.