Comparative investigation between fiber laser and disk laser: Microstructure feature of 2219 aluminum alloy welded joint using different laser power and welding speed

In this investigation, the 2219 aluminum alloy sheets with a thickness of 1.5 mm are welded by different types of lasers. By analyzing the macro-morphology and microstructure of the weld obtained by two different laser welding methods, the characteristics of welding aluminum alloy by using these different lasers are studied. The results indicate that under the gravity of molten pool and different laser power densities, the weld seams (WS) welded by fiber laser and disc laser are in X-shape and Y-shape respectively. Besides, under the influence of Marangoni convection, the equiaxed fine grains of the weld are brought into the middle part, forming a small and regular equiaxed crystal zone (EQZ). It is found that the widths of the WS and the heat-affected zone (HAZ) obtained by fiber laser are both wider than those welded by disc laser. The grain size of columnar dendrites and equiaxed dendrites in the WS welded by fiber laser is coarser than that welded by disc laser. The tensile strengths of disc-laser-welded joints are also higher. In short, disc lasers are more suitable for high-power laser welding aluminum alloys.