Optimization Analysis of Ultrasonic Welding of Copper/Aluminum Electrode Lug Using Response Surface Method

The ultrasonic welding test of lithium battery copper/aluminum electrode lug dissimilar metal was designed by response surface method. A multivariate nonlinear regression mathematical model was established by using the stepwise regression method to screen out the significant factors affecting the responses. The SEM, EDS, XRD, 3D depth-of-field microscopic analysis and micro-hardness tester were used to study the variation of microstructure morphology, phase structure, depth of field and hardness of copper/aluminum welded joints under optimal parameters, and to understand the mechanism of connection and intermetallic compounds (IMCs) generation. The results show that the influence of various process parameters on the tensile load has a very complex interaction, and the interface achieves no defect connection under optimal parameters. High strain rates accelerate the precipitation of Cu9Al4, CuAl and CuAl2 IMCs phase at the interface, and its thickness is about 8 μm. The plastic deformation propagates throughout the thickness of the foil, and the severe plastic deformation promotes the proliferation of dislocations. A transition layer consisting of nanocrystalline and amorphous phases is formed. The strength of the workpiece connection depends on the combined effect of mechanical interlocking, transition layers and element interdiffusion. © 2019, Materials Review Magazine. All right reserved.