Research On Ultrasonic Welding Of Cu/SS With Ni Interlayer

With the progress of modern industry and science technology,single material can no longer satisfy the requirements of manufacturing industry.Composite workpieces which are prepared by dissimilar materials can not only meet the requirements of structural strength,but also contribute to the improvement of economic benefits.The Cu/SS composite workpieces combine the excellent properties of Cu and SS,which can not only solve the shortage of Cu resources,but also deal with the diversification of structural requirements.Numerical simulation of the Cu/SS ultrasonic welding joints were carried out in this paper,and analyzing the law of influence of different welding parameters on the temperature and stress of the interface of joints,and revealing the characteristics of heat generation by interfacial friction and plastic deformation.In the meanwhile,the interface formation,microstructure and mechanical properties were systematically investigated.The obtained results of finite element analysis showed that the distribution of the interface temperature was not uniform.When welding parameters promoted,the level of interface stress gradually increased.The area of the high temperature area of the Cu plate was larger than that of the SS plate.The internal stress of the Cu plate was also more than that of the SS plate.The simulated peak temperature and maximum stress of the interface of joints with an interlayer of the Ni foil were higher than those of joints without interlayer.The simulated peak temperature and maximum stress value of the interface of joints when the interlayer's thickness was 20?m were higher than those of joints when the interlayer's thickness was 30?m.The test results showed that when the energy was in the range of 1600J?2400J,as the energy gradually increasing,the tensile shear first increased and then decreased,which could reach the peak when the energy was 2000 J,and the average tensile shear was 1218.33 N.As the energy increased,the fracture mode of joints changed from interface fracture to base material fracture.The hardness of the interlayer of the Ni foil was significantly higher than that of Cu but lower than that of SS.The change of energy exerted no obvious effect on the hardness distribution of joints.The interface structure mainly included: Cu solid solution,Ni solid solution and austenite.When the static pressure was in the range of 0.2MPa?0.3MPa,as the static pressure increased,the tensile shear showed a trend of firstly increasing and subsequently decreasing.When the amplitude was in the range of 7.5?m?9.5?m,as the amplitude increasied,the tensile shear gradually increased.The associativity of joints with an interlayer of the Ni foil made better performance than that of joints without interlayer.The maximum tensile shear(1261.6N)of joints when the interlayer's thickness was 20?m was larger than that(1174.3N)of joints when the interlayer's thickness was 30?m.With an interlayer,the diffusion distance of atoms at the interface of joints was larger than that of joints without interlayer.The diffusion distance of atoms at the interface of joints when the interlayer's thickness was 20?m was larger than that of joints when the interlayer's thickness was 30?m.In addition,the diffusion distance of atoms of the Cu/Ni interface was larger than that of the Ni/SS interface.Under the current test conditions,more suitable welding parameters were obtained.The thickness of the interlayer of the Ni foil was 20?m.The energy was2000 J.The static pressure was 0.25 MPa.The amplitude was 9.5?m.