Research On Friction Stir Weld Of 7075 Aluminum Alloy

With modern industrial structure of gm vehicle quality,intensity,and the requirement of machining cost and service life is increasing,high strength aluminum alloy is widely used in the vehicle.The weld porosity,weld thermal crack,deformation and softening of joints are related to factors such as the physical properties of aluminum alloy,which is difficult to prevent and eradicate,which affects the wider application of aluminum alloy products in the manufacture of high speed trains and so on.Friction stir welding(FSW)is a new kind of solid phase connection technology,the poor weldability of metal and the welding of dissimilar metals has a certain advantage,can effectively avoid the various defects in the process of welding.Therefore,it is of great theoretical significance and practical value to study the structure and performance of7075 aluminum alloy FSW joint.7075 aluminum alloy is widely used in aerospace field,it is a kind of material with high strength,strong corrosion resistance and low density.Based on a large number of relevant literature,this paper first expounds the basic principles of friction stir welding process,and lists the advantages and disadvantages compared with conventional welding,studies of literature to extract FSW related domestic and foreign research present situation and development prospect.addition,it has been found that the mechanical properties of the joints also have a certain relationship with the ratio of the welding speed and the rotation speed.When the ratio is a certain value,the mechanical properties of the joint gradually increase with the increase of the rotation speed,reach a maximum value,and then gradually decrease.There is a similar relationship between the mechanical properties of the joint and the ratio.The high speed and high quality friction stir welding of 7075 aluminum alloy plate with 3mm was realized through a large number of experiments of process parameters.The tensile strength of the weld is 80% of the base material.The effects of different welding parameters such as rotating speed of agitator head,welding speed and their ratio on FSW joint of 7075 aluminum alloy were analyzed.For the relevant properties of 7075 aluminum alloy,targeted in a series of experiments,mainly includes: friction stir welding process experiment is discussed,and metallographic test,the tensile experiments,experiment and its hardness material bending test,photoelectron spectroscopy analysis of the experiment.According to the above experiments,the following conclusions can be drawn: when the technological parameters of welding7075 aluminum alloy are properly set,the beautiful and defect-free joint structure can be obtained.If the process parameter setting of 7075 aluminum alloy is not reasonable,the weld structure is prone to groove,flying edge and tunnel type defects.The above experiments,and found that the mechanical properties of the weld metal(for example:the material of elongation and tensile strength)with the relationship between process parameters,when other metal welding process parameters to determine the value,the mechanical properties of the welded joint first increases with the increase of welding speed,after reaching a maximum value,its mechanical properties with the increase of velocity.In addition,comparing the experimental results,the ratio of mixing head rotation speed and welding speed on the mechanical property of weld metal will also impact,under the condition of fixed the ratio,the mechanical properties of weld microstructure of optimization,with stirring head speed increase after reaching the maximum,then gradually decline.At the same time,the mechanical properties of metal welded joints are also related to the ratio.