Research On Strengthening Micorstructure And Properties Of Laser Welded Joints Of 6016 Aluminum Alloy

6016 is a kind of aluminum alloy material with good comprehensive performance.Due to its advantages,it has great development potential in automobile lightweight,energy-saving,and environmental protection.However,the problem of joints softening restricts its application.For this reason,dissimilar 6016 aluminum alloys were welded by using laser welding,the microstructure,mechanical properties and corrosion resistance of the joints were studied in this article.This article also analyzed the influence of post-weld heat treatment and ultrasonic impact treatment on the structure and performance of the joint.Correspondingly,it will have far-reaching significance to expand and develop the application potential of 6016 aluminum alloy in automobile lightweight.First,6016 aluminum alloy of the same grade and different processing states were welded by using of YLS-10000 Laser System with high power(10 k W),and the better quality welds were selected.Secondly,heat treatment and ultrasonic impact treatment were performed on welded joints,and XRD analysis,microstructure analysis,microhardness analysis,tensile performance analysis,and corrosion resistance analysis were carried out.Compared with the untreated joints and original plates,explored the effects of post-welding heat treatment and ultrasonic impact treatment on the structure and performance of laser-welded joints.The results show that the grain size of each area of the untreated joints was very different.The center of the weld was a small and uniformly distributed equiaxed crystal;between the fusion zone and the center of the weld was a coarsely subdivided layer of equiaxed crystals,and there were many precipitated phases at the layer;the fusion zone was coarse columnar crystals growing perpendicular to the fusion line,there were liquefaction cracks near the fusion line,6016T6 base material was more on one side,6016T6 base metal is fine equiaxed grain,6016 Fbase metal is banded structure along the rolling direction.After heat treatment,the liquefaction cracks in the fusion zone were weakened,and the equiaxed crystal structure and composition segregation of coarse and fine layers disappeared.The joint effect was the most obvious after solution at 530°C for6 h and water quenching,and artificial aging at 180°C for 3 h;after ultrasonic impact treatment,the transition of the weld toe was smooth,the stress concentration disappeared,the surface of the weld undergoes violent plastic deformation,and the grain was refined.The joint effect was the best after the initial impact load of 50 N and the full coverage impact for 5 times.Through the comparison of mechanical properties,the mechanical properties of the welded joints were lower than those of the base metal,and the joints softened.After heat treatment and ultrasonic impact treatment,the mechanical properties of the joints were improved to varying degrees,among which the heat treatment parameters were 530?×6h+180?×3 h and impact parameters were the best mechanical properties of the joint after the initial impact load was 50 N and the impact was treated for 5 times.By comparing the corrosion resistance,the electrochemical inhomogeneity of the microstructure and the homogenization of the chemical composition in the weld zone after heat treatment and ultrasonic impact treatment were improved,and the corrosion resistance was significantly improved compared with the welded joint.