Numerical Simulation Of Temperature Field And Flow Field Of Al/Mg Friction Stir Welding Based On Coupled Eulerian-lagrangian Approach

With the development of economy and society,green economy,energy saving and emission reduction have become the general trend of social development.This concept also has an impact on the selection and processing of materials,especially in terms of material lightweighting and bongding.Among them,aluminum alloys,magnesium alloys and other lightweight materials are widely used.Therefore,it is inevitable to encounter the bongding issue of Al alloy and Mg alloy.Compared with traditional fusion welding,preferable joints can be obtained by using Friction Stir Welding(FSW)to weld Al/Mg dissimilar alloys.For Al/Mg dissimilar alloy FSW,the key is to control the formation of intermetallic compounds and form a good mechanical bite.The regulation of temperature field is an important means to control the formation of intermetallic compounds.The flow of two materials is the key to form an effective mechanical bite.Therefore,the study of FSW temperature field and flow field is of great significance.Based on the coupled Euler Lagrangian(CEL)method,this paper will establish the numerical simulation model of FSW docking between 5A06 aluminum alloy and AZ31 B magnesium alloy with complex morphology of stirring needle,and study the distribution law of FSW temperature field and flow field characteristics of Al / Mg dissimilar metals through numerical simulation.The monitoring results of kinetic energy and internal energy ratio in the calculation process show that the reliability of the numerical model meets the requirements.The comparison of the characteristic point temperature cycle curve of the experimental measurement and simulation results shows the effectiveness of the model,and the model can reasonably simulate the temperature field distribution in FSW.In general,the temperature of Al side(as)is higher than that of Mg side(RS)in the whole welding process.When the rotating speed is fixed,the temperature at the weld changes slightly with the increase of welding speed;when the welding speed is constant,the temperature at the weld increases obviously with the increase of the welding speed.During the welding process,the temperature gradient on the Al side is less than that on the Mg side,and the temperature gradient in front of the mixing head is greater than that in the rear.In this paper,the flow of materials in the FSW process of Al/Mg dissimilar metals is analyzed by using the method of tracer particles.It is found that due to the large mesh of the model and the use of mass scaling,the boundary between Al and Mg in the simulation results is 1mm away from the weld center than the actual results,but the weld morphology is close to the test results on the whole.The simulation shows that the fluidity of the material on the Al side is significantly better than that on the Mg side.The material on the forward side is stirred by the mixing head,and most of it is finally accumulated near the weld.The material stirred on the forward side mainly falls near the weld center at the rear of the mixing needle.At the same time,it is found that when the rotating speed is fixed,the size of the material mixing zone at the weld changes little with the increase of the welding speed;When the welding speed is constant,the material mixing zone at the weld increases obviously with the increase of the welding speed.