Growth Mechanism Of Copper/Aluminum Solid State Interface IMC

In recent years,the gradual maturity of composite plate technology has attracted a lot of attention.Due to its good conductivity,heat conduction and corrosion resistance,copper aluminum composite plate is widely used in automobile manufacturing,household goods,power system,metallurgical equipment and other industries.The common composite methods are explosive welding,hot rolling,cast rolling,etc.in the above composite methods,a large number of intermetallic compounds will inevitably be produced at the interface of composite plate.Because the intermetallic compounds are hard and brittle,the mechanical properties of composite plate will be greatly reduced.Therefore,in order to improve its mechanical properties,it is necessary to study the growth mechanism of intermetallic compounds at the interface,so as to carry out Thickness control to reduce its harmIn this paper,the cold-rolled copper aluminum composite plate was used as the research object.The intermetallic compounds with different thickness were obtained by changing the annealing temperature and time.The annealing interface of Cu/Al was observed and analyzed by SEM,EDS and XRD.The results show that there are three kinds of IMCs:Al₂Cu,Al Cu and Al₄Cu₉ from the Cu side to the Al side.The thickness is measured by Image J software.Finally,the relationship between the thickness and the time is drawn by Origin,and the growth mechanism of the intermetallic compound at the copper-aluminum solid-solid interface is discussed.The results show that there are two diffusion mechanisms of Al₂Cu,alcu and Al₄Cu₉,which are the early reaction control stage and the later diffusion control stage.The growth kinetic models of Al₂Cu,Al Cu and Al₄Cu₉ under the two mechanisms were calculated.The reaction activation energy of Al₂Cu was 57.4 k J/mol,the diffusion activation energy was 44.5 k J/mol;the reaction activation energy of alcu was 64.3k J/mol,the diffusion activation energy was 53.4 k J/mol;the reaction activation energy of Al₄Cu₉ was 60.3 k J/mol,the diffusion activation energy was 48.1 k J/mol;the reaction activation energy and diffusion activation energy of the whole layer were 62.0 and 52.7 k J/mol,respectively.The results show that in the reaction control stage,the thickness of IMC increases slowly,while in the diffusion control stage,the thickness of IMC increases rapidly and finally slows down.The fracture of intermetallic compound can be judged by cup forming of 100*100*3mm cold rolled plate after heat treatment and observing the Cu/Al interface at different positions after cup forming.The results show that the crack preferentially propagates at the interface of Al₂Cu/Al Cu.When the thickness of Al₂Cu layer is more than 5?m and the total thickness is more than 10?m,the crack perpendicular to the Cu/Al interface is easy to appear at the position of blank holder and arch,and the crack along the Cu/Al interface is easy to appear at the middle and upper part of bending.The damage simulation of Cu/Al composite plate after convex forming was carried out by the finite element analysis software Abaqus.The stress at the interface of Cu/Al was analyzed by the software and compared with the experimental results.The simulation results show that the shear strength of Al₂Cu layer is about 134Mpa,that of Al Cu layer is about 210Mpa,and that of Al₄Cu₉ layer is about 240 Mpa.