Friction Stir Welding Of 7XXX Series Aluminum Alloy Sheets And Rolling Deformation Behavior Of The Joints

7XXX series aluminum alloy is a high-strength aluminum alloy containing zinc,copper and other elements.In the past,it was mainly used in aerospace materials.In recent years,it has also been used more in electronic products.It is an important industrial basic material,and its plate is in great demand in the market.The application of friction stir welding to 7XXX series aluminum alloys can better show the excellent characteristics of the material.Compared with traditional welding,friction stir welding has obvious advantages.The structural parts of 7XXX series aluminum alloy are connected by friction stir welding.In recent years,research in this area has made great progress.However,combining the two separate processes of friction stir welding and rolling,no work has been reported in this field,and it is not clear how the microstructure and property changes in the rolling process of the welding joint connection zone.In this paper,the friction stir welding process is applied to the actual production of rolling,and the deformation behavior of welded joints under different rolling reductions is studied.Consider using friction stir welding instead of traditional welding to achieve continuous rolling,which can not only increase the length of the single coil of aluminum alloy,but also achieve continuous headless rolling,improve the productivity of aluminum alloy plate and improve product quality.In this paper,7XXX aluminum alloys connected by friction stir welding were studied,and the microstructure and properties of the welded joints of 7075 and 7050 aluminum alloy sheets after rolling were focused.Explore the feasible conditions of friction stir welding for continuous rolling production of aluminum alloy.The results show that a friction stir welded joint with beautiful appearance and no defects inside can be obtained,when the stirring head speed is 1400 rpm,the welding speed is 15 mm/min,the shoulder pressure is 3 k N,and the inclination angle is 2°.And the subsequent rolling can be ensured.In the tension rolling process,the 7XXX aluminum alloy does not have rolling defects such as sheet fracture,and the welded joint is plastically deformed together with the base material.And as the thickness of the sheet is reduced,the features at the welded joint gradually disappear,the microstructure of each region becomes more uniform and the difference of mechanical properties is reduced.It is indicated that continuous rolling of the 7XXX aluminum alloy can be achieved by this process.Therefore,it is supposed that utilization of the friction stir welding to achieve continuous rolling can increase the length of the aluminum alloy single coil,and realize continuous headless rolling and then increase the productivity of the aluminum alloy.In consideration of the connection requirements for the production of different brand products,friction stir welding was performed on aluminum alloy plates of different brands with the same thickness.It was confirmed that 7XXX series aluminum alloys can be connected by friction stir welding.However,due to the different thermophysical properties of different grade alloys,it will affect the metal structure of the weld zone and increase the heterogeneity of the structure.By measuring the temperature field during the welding process,it was found that the two metals have the same trend during the welding process.However,the peak temperature is different,indicating that dissimilar metal welding has asymmetry.By using different welding mold materials and adjusting heat dissipation conditions,the effect of asymmetry in welding can be improved.