Aluminum Alloy Sheet Of Friction Stir Welding Deformation Mechanism And Control

Recently, as the rapid development of aerospace industry, the joining technique about aluminum alloy thin-walled structures also needed rapid improvement. For higher security and technological considerations, invented more reliable connective technique has became a top priority. As a non-fusion welding, friction stir welding technology can effectively avoid t burn-through and poor performing of weld joints, so FSW is particularly suitable for welding of aluminum alloy. However, Welding deformation is still very serious in FSW. Therefore,we should solve this problem as soon as possible.Generally, welding deformation includes mismatching deformation, buckling deformation and flexure deformation. It is concluded that the distribution of residual compressive strain and longitudinal tension stress of the area next to weld seam, along the thickness direction, is asymmetrical, which is the essential reason of flexure deformation. And excessive longitudinal residual compressive stress is the essential reason of buckling deformation. In this paper, we added a synchronic water-cooled device based on the conventional friction stir welding, which could regulate temperature and reduce the residual stresses in the welding process and welding deformation of welding joint.Then we verified the feasibility of technology, analyzed the effects of different cooling intensity by the numerical simulation of welding temperature field on COMSOL, We found that the simulation results are consistent with the experimental results.Moreover, we complete single pass of 2024-T4 by friction stir welding based on numerical analysis. The results showed that using suitable intensity cooling water could regulate the temperature field, reduce residual stress and inhibit welding deformation effectively. When the cooling water pressure is 0.4MPa, the effect of temperature regulation is best and joints' macro-deformation is lowest, while the difference between top and bottom joint surface residual stress is lower than 36MPa, deflection is less than 0.1mm, deformation of the weld sections is 1mm. Then, we completed comparative experiment of 2524 at different welding process, such as using stainless steel worktable, adopting ultrasonic stir compound welding process and so on, and then further analyzed the regularity of deformation of FSW joints.Father more, we completed the comparison of 2024 long paint at different welding parameters. When the cooling water pressure is 0.4MPa, joints' macro-deformation is lowest, deformation of the weld sections is 4mm.And we found when the rotation speed is 2100r/min and welding speed is 120mm/min, the weld joints'mechanical intensity, which exceeded 80% of the base metal, is strongest.This paper holds that synchronic water-cooled FSW process, which could produce the best weld joints with high strength and small deformation, is particularly suitable for the connection of light metal shell structure.