Numerical Simulation And Experimental Study On Laser Welding Of T-joint TC4 Titanium Alloy

Titanium alloy has been widely used in aerospace field because of its many excellent physical and chemical properties.There are usually two ways to connect aircraft skins and stiffeners : riveting and welding.Compared with riveting,welding can effectively reduce the weight of the structure,improve the air tightness and the mechanical properties of the structure.In a variety of welding processes,for titanium alloy materials,laser welding has the advantages of high processing efficiency,energy concentration and small processing deformation,and has been widely used in industrial production.In this paper,the laser welding experiment of TC4 titanium alloy T-joint was carried out by continuous laser welding platform.The macroscopic morphology,metallographic structure,Vickers hardness and residual stress of the welded joint were measured,and the forming quality under different welding parameters was analyzed.The results show that when the laser power is constant,if the welding speed decreases gradually,the penetration depth and width of the molten pool will gradually increase.When the welding heat input exceeds 100 J / mm,oxidation occurs on the weld surface.By analyzing the Vickers hardness of the welded joint,it can be found that the Vickers hardness of the weld heat affected zone is the highest,and the Vickers hardness of the fusion zone is slightly higher than that of the base metal.The laser welding process of TC4 titanium alloy with T-joint was simulated by ABAQUS finite element software.The temperature field and stress field of T-joint in the welding process can be obtained,and the residual stress of welded joint measured by Xray stress tester is basically consistent with the results obtained by simulation calculation,which verifies that the finite element model established in this paper has high accuracy.Finally,the evolution process of temperature field and stress field under different welding sequences is analyzed.When the welding speed is lower than 0.9 m / min,the node temperature will show a significant upward trend,and compared with the first weld,the laser power has a greater influence on the node temperature of the second weld.When the welding heat input is less than66 J / mm,the longitudinal residual stress inside and near the weld is symmetrically distributed.When both sides of the weld are welded in the same direction at the same time,the longitudinal residual stress in the vertical weld direction is the smallest;when the reverse welding is carried out at the same time,the transverse residual stress in the parallel weld direction is the smallest.Therefore,by considering the stress of the welded structure in the practical application,selecting the appropriate welding sequence can have a good reference for the application of Tjoints in the aerospace field.