Study Of Microstructure Properties And Welding Temperature Field Numerical Simulation For Laser Welded Joints Of Dissimilar Aluminium Alloy

At present,lightweight is the main trend of locomotive and vehicle manufacturing industry.Because of its advantages of high specific strength and low density,aluminum alloy has become an important material for lightweight design.5182 aluminum alloy and 6061-T6 aluminum alloy are two kinds of materials widely used in automobile industry,Problems will inevitably arise in the welding of this two aluminium alloys.However,problems such as blowholes of aluminum alloy laser welding restrict its development,which are urgent problems to be solved in current experiments and engineering practice.Therefore,the optimization of laser welding parameters of dissimilar aluminum alloys has important practical significance for its application in engineering practice.In this paper,5182 aluminum alloy and 6061-T6 aluminum alloy with a thickness of4 mm were selected as the research objects to explore the influence rules of technological parameters on the forming,microstructure,mechanical properties and corrosion properties of laser welded joints.ABAQUS software was used to simulate the temperature field.Conclusions are as follows:The technological parameters have an important influence on the surface forming and section morphology in laser welding of dissimilar aluminum alloys.Through optimization test,the optimal technological parameters are obtained as follows: P=4.2k W,(35)f =+3mm,v=30mm/s.The joint has satisfied shape and good mechanical properties under this technological parameters.The crystal structure near the fusion line is columnar and the growth direction is perpendicular to the fusion line.The center of the weld is fine equiaxed grain.The heat affected zone of dissimilar aluminum alloys laser welding joint is narrow because of the rapid heating and cooling of laser welding.XRD and SEM results showed that Mg2Al3 was precipitated on the side of 5182 aluminum alloy and Mg2 Si was precipitated on the 6061-T6 side.The microhardness of laser welding joint center of dissimilar aluminum alloys was the lowest,which was significantly different from 6061-T6 aluminum alloy and basically consistent with 5182 aluminum alloy.The microhardness value will change in the heat-affected zone due to the effect of aging hardening.In the tensile test,the fracture position of the specimen are all in the weld zone,in which the laser power had the most significant influence on the tensile properties of the joint,and the tensile strength of the joint could reach up to 70.26% of the tensile strength of 5182 aluminum alloy and 64.37% of that of 6061-T6 aluminum alloy.The fracture shows a 45°crack,and the fracture type belongs to ductile fracture.In the electrochemical corrosion test,it was found that the corrosion resistance of weld under the best parameters was between the two base materials.The intergranular corrosion resistance of the joints is different in each area.The intergranular corrosion resistance of the weld center is the strongest,followed by the heat-affected area,and the base material is the worst.In the temperature field simulation test of dissimilar aluminum alloys laser welding,the thermal cycle curve of each characteristic point is consistent with the temperature curve output by the paperless recorder in the actual test.The peak temperature of the weld center at the end of welding is the maximum value in the whole welding process.The range of temperature field cloud map on the 6061-T6 side is larger,the temperature gradient is less than 5182 aluminum alloy.5182 aluminum alloy reaches peak temperature more faster.The weld width increases with the increase of heat input.the joint section morphology is basically consistent with the actual welding,and the vertical section pool is semi-circular,which verifies the accuracy of the model.