Study On The Interface Diffusion Process Of Cold Rolling Cu/Al Clad Metal Sheet In Annealing Process

Cu/Al thermometal composite material has outstanding property with highconductivity, good thermal conductivity and corrosion resisitance. It’s an excellentcandidate which to be applied to large transmission and transformation equipments insteadof pure Cu. But in the working time, it is quite easy for the metal sheet forming fragilityphase on the interface because of heat effect. The key is the fragility phase will do harm tothe interface bond strength, mechanical property and some related electrical characteristics.For this purpose, this thesis studied on the growth rule of intermetallic compounds on theinterface layer in annealing process of cold rolling Cu/Al clad metal sheet.The Gibbs energy of the end border solid solution （χ[Al（Cu）] and α[Cu（Al）]） and bothGibbs energy and formation Gibbs energy of the five kinds of intermetallic compoundwhich may form in low temperature were calculated,with different thermodynamic models.Besides, Al₂Cu was predicted to be the first compound on the Cu/Al diffusion layer bymeans of the Effective heat of formation model.The results showed that, temperature is the primary factor to the interface and phasestructure of the cold rolling Cu/Al clad metal sheet, the subordinate factor is holding time.The number of the interface diffusion layer increases from one to three with longer holdingtime in the same temperature. Then, that number will be steady at that moment but thethickness of every layer will increase. What’s more, the rate of the thickness rise willdecrease with extension of holding time and the diffusion layer will stop growing at last.There were2diffusion layer at most for250℃holding100h and3diffusion layer most for300℃、350℃、400℃、450℃and500℃. The composition of the diffusion layers arealmost same. They are the first phase Al₂Cu on the Al side, the second compound Al4Cu9on the Cu side and the last one AlCu in the mid-layer. That is to say the tested formationsequence of the intermetallic phases was Al₂Cu （Al side）, Al4Cu9（Cu side） and AlCu.Combined with different tested method, the mutual diffusion coefficient D, diffusion activation energy Q and diffusion constant D0was calculated. Finally, the functionalrelationship of diffusion coefficient-thickness of diffusion layer-temperature-holding timewas established.