Unravelling asymmetrical microstructure evolution and tensile fracture mechanism in laser welding of dissimilar 2219/2195 aluminum alloys

The laser welding of dissimilar 2219 Al–Cu and 2195 Al–Li alloys is a significant attempt in the fabrication of rocket propellant tanks, aiming at the escalating demands for weight reduction and cost efficiency. The variances in microstructure evolution for 2219/2195 aluminum alloys laser welded joint deserves thorough investigation because it certainly results in the discrepancies in mechanical property In this paper, the temperature field, microstructure, element distribution, grain orientation, and texture on both sides of the laser welded joint were comprehensively investigated through a combination of simulations and experiments. The tensile strength was tested and the fracture mechanism was analyzed based on the microstructure characteristic. It is found that the wider columnar dendrites zone is generated due to the large temperature gradient from on the 2195 Al–Li alloy side. The grain orientation of the non-dendrite equiaxed zone (EQZ) and columnar grain near the fusion line are significantly influenced by the grain orientation of base metal (BM). On the one side of 2195 Al–Li alloy, the majority of grains feature diameters predominantly within the 3–6 μm range. The region in the vicinity of fusion line on one side of the 2195 Al–Li alloy has the weakest performance. It is deduced that the poor tensile property on one side of the 2195 Al–Li alloy is not only attributed to the loss of Mg and Li elements, but also owing to the evolution of texture. The rotated goss texture with high intensity is formed in EQZ near the fusion line on one side of 2219 Al–Cu alloy.