Numerical Simulation And Welding Performance Of Friction Stir Welding Of 5083-O Aluminum Alloy

After 30 years of development,friction stir welding technology has played an increasingly important role in automobile,rail transit,aviation and other fields,especially for the traditional fusion welding of aluminum magnesium alloy and other metals which are difficult to obtain reliable welding performance.The application of friction stir welding technology can avoid pores,sand holes and other defects,improve joint strength,and make a higher demand for structural strength It is possible to use aluminum alloy instead of steel to realize the lightweight in the situation of high-speed production.Friction stir welding(FSW)is a process of thermal mechanical multi field coupling,which involves complex changes of material properties.The lack of research methods makes people not fully understand the mechanism of this process.Therefore,the FSW process of 5083-O aluminum alloy was studied comprehensively in this paper.Based on the coupled Eulerian Lagrangian method,an efficient finite element simulation model is established by using the mass scaling technique for the first time,which greatly improves the simulation efficiency.The modified Coulomb friction contact relationship is established,and the temperature field under different welding processes is obtained.The correctness of the model is verified by comparing with the experimental results.The results show that: the temperature of the forward side is higher than that of the backward side,which is related to the selected welding process;the peak temperature of the weld surface is not invariable,and the temperature change trend is different with different welding processes;the peak temperature increases with the increase of the rotating speed,but the growth rate decreases,and the maximum temperature is lower than the melting temperature;the peak temperature decreases with the increase of the welding speed But if you decrease the speed,it will also decrease.In this paper,different FSW welding processes were used to weld 8mm thick 5083-O aluminum alloy plate,and the temperature changes of forward side and backward side were measured during the welding process;tensile tests were carried out on the upper and lower layers of the joints welded by different welding processes,and it was found that the mechanical properties of the upper and lower layers of the weld were significantly different:the mechanical properties of the lower layer of the weld were excellent and stable,both exceeding 288MPa;the tensile strength of the lower layer of the weld was higher than288 MPa The mechanical properties of the upper layer of the weld are closely related to the welding process.When the rotation speed is 1500 rpm and the welding speed is 300 mm /min,the tensile strength of the upper and lower layers of the weld exceeds that of the base metal,and the maximum is 310 MPa.The hardness curve perpendicular to the weld direction is W-shaped,and the hardness of the weld center is high due to the fine grain strengthening effect,while the hardness of the heat affected zone is small Welding process related.The fracture morphology was observed by SEM.It was found that too high welding speed or too fast welding speed would lead to poor toughness of the joint.