基于X形正反螺纹搅拌针的搅拌摩擦搭接焊材料流动及其影响下的接头成形规律OACSTPCD

Making the pin largely plunge into the lower plate is a common process of friction stir lap welding(FSLW)tech-nology,but the induced hook with an up-bending morphology reduces the effective sheet thickness of the joint,which is not conducive to obtaining the joint with high bearing capacity.In this paper,in order to realize the down-bending morphology of hook,the X-shaped reverse-threaded pin was self-designed.By this pin,the material flow behavior was simulated numeri-cally during FSLW,and the relationship between material flow and joint formation was studied.The results showed that un-der the driving action of pin,the materials in stir zone(SZ)top and SZ bottom respectively flowed downwards and upwards and then accumulated in the middle of SZ,and these accumulated materials had a flowing trend along the horizontal direc-tion.When the material accumulated zone was located above the original lap interface,the hook bent downward and the SZ width was enlarged.At the rotating velocity of 800 rpm and the welding speed of 300 mm/min,the 2024-T4 aluminum al-loys FSLW joint had a 299.6 MPa tensile strength,and this value was greatly higher than the reported tensile strengths of 2000 series aluminum alloys FSLW joint.