An investigation on cold roll welding of copper to aluminum using electrical resistivity

To manufacture a high quality cold welded Al/Cu electrical transition joint , it is essential to understand the relationship between bond strength, bon d morphology, and electrical resistivity of the bimetal. The samples of Al and Cu bimetal were produced by a cold roll pressure welding process. The d ifferent strengths of the metallic bond between Al and Cu strips were achie ved by the different reductions in thickness. The peeling force per unit le ngth of bond and the resistivity of the samples were measured. The threshol d reduction in thickness to start the metallic bond between the Al and Cu s trips was characterized. The dependence of bond strengths of different samp les on the morphology of the interface was discussed. The effect of short t ime annealing on the relaxation of the clipping stress at the interface and the bond strength was assessed. The resistivity and bond strength have a s imilar trend as a function of the thickness reduction. Based on these resul ts a calibrated diagram was established for a nondestructive evaluation of the bond soundness by an electrical resistivity test.