Research On Friction Stir Diffusion Lap Welding Process Based On Convex-Vortex Shoulder

As one of the important joint configurations in the friction stir welding(FSW),lap joint is widely applied in the aerospace industry.In this paper,three types of pin are designed and manufactured from the perspective of optimizing the overall shape of pin: Two convex-vortex pin tool,Four convex-vortex pin tool,Six convex-vortex pin tool.AA2024 was choosed as research subject,and the effects of the overall shape of pin on the cross-section morphology and lap shear failure performance of the lap joints were researched.Besides,FLUENT was also adopted to analyze the material flow during welding process,and corresponding physical models of material flow were also established.According to the experimental results,it was found that:(1)Material on AS migrates to RS under the shearing actions of shoulder and pin,which leads to the accumulation of material on RS.The material accumulated in the SZ center squeezes the lap interface during welding process,which leads to that the middle part is thinner than other regions of lap interface.(2)The SZ bottom can be effectively enlarged with increasing the number of convex-vortex pin because pin-driven material flows become more intense.(3)The lap shear loads varying with rotating speeds present different laws under different rotational tools due to the appearance of microcrack in the lap interface.The maximum lap shear failure load of 19518.34 N can be attained by S-tool under rotating speed of 500 rpm.The minimum lap shear failure load of 10526.49 N can be attained by T-tool under rotating speed of 700 rpm.(4)Tensile fracture mode is attained under the reasonable combination of tool geometries and process parameters,which indicates better diffusion bonding between upper and lower sheets.Shear fracture mode is also attained,and these two fracture modes both present a ductile fracture.