Microstructure And Properties Of Continuous Drive Friction Welding Of 6061-T6 Aluminum Alloy And T2 Copper

Continuous Drive Friction Welding(CDFW),a special welding technology,is now playing an increasingly important role in automobile manufacturing,rail transit and other manufacturing fields.Aluminum alloys used in China can reduce the weight of the structure.Welding is a process of thermal-mechanical multi-field coupling,which includes relatively complex material property change.People do not completely comprehend the alteration mechanism of materials during the welding course.The changes of microstructure and properties of T6 aluminum alloy and T2 copper in the CDFW process are investigated.1.Using the two-dimensional axisymmetric thermomechanical coupling numerical simulation method,the process parameters are coupled into the calculation model,and the apparent temperature of the bar is acquired.Compared with the temperature measurement results,it is found that the numerical value is close,which verifies the accuracy of the simulation results.Out of the welding interface temperature,with the increase of the rotation speed,the interface temperature has been increasing,the temperature of the weldment center and flash is low,the temperature of the weldment is the highest at 2/3R from the center of the circle,and there is a temperature gradient in the axial direction of the weldment.On both sides of the seam,the farther away from the seam,the lower the temperature value.2.In this paper,6061-T6 aluminum alloy and T2 copper bar with a length of 100mm and a diameter of 18mm are welded by different speed process parameters.During the process,the apparent temperature of the bar is gauged.In the tensile test,when700rpm?1200rpm,the tensile strength firstly Increases and then reduces,and At 1000rpm,the tensile strength is the largest,which is 212MPa,accounting for 73.1%of the strength of the base metal on the aluminum side.3.Test the hardness perpendicular to the direction of the weld,including both sides of copper and aluminum,the hardness curve is"W"shape,the center of the weld is the highest due to the factor of the intermediate metal compound(IMC),with the increase of rotation speed,the hardness of the weld increases all the time,and the aluminum side has the highest hardness.The hardness of the dynamic recrystallization zone(DRZ)is second only to that of the weld.With the increase of the rotational speed,the hardness of this area increases first and then decreases.The hardness of the heat affected zone(HAZ)is the smallest,and the hardness of this area decreases with the increase of the rotational speed.4.According to the fracture morphology,at 700 rpm,the copper side fracture has a tear edge and is surrounded by cleavage surfaces,and the tear edge is covered by aluminum elements.At 1000rpm,the copper-side fracture has a large number of dimples,and the dimples are covered by a large amount of aluminum elements.At 1200rpm,the copper-side fracture is flooded with cleavage planes.In the range of 700rpm?1200rpm,the weldments all show brittle fracture characteristics.5.The IMC thickness test of the welding interface shows that the thickness of the IMC increases continuously with the increase of the rotational speed.The analysis of the element composition at the welding seam shows that there may be Al₂Cu,Al Cu,and Al4Cu₉.6.Observe the metallographic structure on both sides of copper/aluminum.There are DRZ,HEAZ,HAZ,flash area(FA),base metal(BM)on the aluminum side,and DRZ,HEAZ,HAZ,and BM on the copper side.HEAZ,HAZ area width has been increasing.The grain size areas on the aluminum side are HAZ,BM,HEAZ,FA,and DRZ from large to small.Among them,the grain size of the HAZ area increases with the increase of the rotational speed,the grain size of the FA(paraxial sleeve)decreases with the increase of the rotational speed and the grain size of the other regions firstly decrease and then increase with the increase of the rotational speed.