Research On Tailor Welding Processing And Tensile Property Of Different Thickness Aluminum Plates By Dual-beam Laser Welding

Laser tailor welded blanks(LTWBs) made of aluminum alloys is an important researching aspect in auto-body manufacturing, which can reduce the auto-body weight and energy consumption. Therefore, the 1.0 and 2.0-mm-thick 5182-O aluminum was taken as base metal for LTWBs of the different thickness aluminum. The effect of defocus,heat input, shielding gas flow, spot distance and energy ratio on the weld appearance were investigated. We also research on the weld geometry, microstructure and mechanical properties of the single and dual-beam laser welding joints. It aims at laying a good foundation for engineering applications.This thesis study the effect of defocus, heat input and shielding gas flow on the weld appearance in the single-beam laser welding. It is found that the front weld appearance is smooth and the back weld appearance is rough when the defocus amount is-2 mm,-4 mm,+2 mm. However, when the defocus amount is-4 mm,-8 mm,-12 mm and +4 mm, both the front and back weld appearance are smooth. As the defocus is constant, the back weld appearance become more and more rough with the heat input decreasing. What's more,the amount of shielding gas flow has no effect on the weld appearance. But, once stopped the supply of shielding gas flow during the laser welding processing, the joints' sag were occurred in the procedure.The dual-beam laser welding processing has been taken on the basis of the singlebeam laser welding processing. The results show that the weld appearance is better when the energy ratio is 68/32. The spot distance has an important influence on the weld appearance, the weld joints from burn-off become to lack of penetration with the spot distance increasing. Also, the weld appearance of the dual-beam laser welding processing is better than the single-beam laser welding processing and has less spatter during the welding processing.Microstructure and mechanical properties of the dissimilar 5182-O aluminum dualbeam laser welded joints have been compared with the single-beam laser welded joints.The results show that the joints of the two welding processing have similar distribution of microstructure. Around the fusion line is columnar zone, and the weld center is equiaxed crystal zone. The EDS test results show that there is evaporation loss of Mg element in thewelding joints and the evaporation extent is the same both in the single-beam laser joints and dual-beam laser joints. The hardness tests indicate that the welding joints' hardness is higher than the base metal. In addition, the tensile test indicate that the single and dualbeam laser welding tensile test specimens all fracture in the thin base metal and the elongation of them are 9.56% and 11.41%.