Research On The Electric Conductivity And Interfacial Thermal Stability Of Cu/Al Clad Plate

Cu/Al clad plate that is produced by clad rolling technique has been the research focus in the field of bus-bar materials for its advantages of not only low bonding resistance of both heat and electricity, but also good ductibility and forming property. However, there are many deficiencies in its research such as the control of process parameter during clad rolling and the subsequent heat treatment, and its effects on the interfacial characteristics and electric conductivity. So the electric conductivity of Cu/Al clad plate and its influencing factors, including thickness, width and contour of the clad plate, the applied voltage frequency, the thickness of copper layer were analyzed using ANSYS software. Also the effects of the temperature and time of heat treatment on the interfacial morphologies, diffusion transitional layer, as well as interfacial peeling and thermal fatigue behavior of the Cu/Al clad plate, were investigated.The results show that with the applied voltage frequency increases from 50 to 1000 Hz, the total electric current density decreases greatly, and the resistance of the Cu/Al clad plate increases obviously. With the increase of copper layer thickness, clad plate thickness and width respectively, the total electric current density increases and the resistance of the Cu/Al clad plate decreases gradually, and the optimal thickness ratio of copper and aluminum is obtained as 0.2 by simulation analysis. Also the contour of clad plate affects its electric conductivity greatly, as for the square edge clad plate, the electric current distributes more regular and concentration level is lighter than that of the round corner one with the same applied current. The electric conductivity of the Cu/Al clad plate is lower slightly than that of pure copper bus-bar, while much more excellent that of pure aluminum one with the same specification, so the clad plate can be used to substitute for the conventional pure copper or aluminum bus-bar.During the heat treatment, the boundary becomes vague and the diffusion transition zone with a certain thickness is formed at the interfacial zone between copper layer and aluminum one for the diffusion of copper and aluminum atoms occurring across the interface, and the thickness of diffusion layer increases with the increases of the heat treatment temperature and time. As the heat treatment temperature increases, the morphology of peeling interface changes from dimple-like to stream-like, and then to pistil-like, and the interfacial peeling behavior changes from ductile peering to brittle one. The composite interface is still of good bonding state after thermal fatigue testing with and without stress, which indicates that the interfacial layer of the Cu/Al clad plate is of good thermal stability.