Evolution of bonding interface in solid-liquid cast-rolling bonding of Cu/Al clad strip

Cu/Al clad strips are prepared using solid-liquid cast-rolling bonding (SLCRB) technique with a d160 mm x 150 mm twin-roll experimental caster. The extent of interfacial reactions, composition of the reaction products, and their micro-morphology evolution in the SLCRB process are investigated with scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD). In the casting pool, initial aluminized coating is first generated on the copper strip surface, with the diffusion layer mainly consisting of alpha(Al)+CuAl2 and growing at high temperatures, with the maximum thickness of 10 mu m. After sequent rolling below the kiss point, the diffusion layer is broken by severe elongation, which leads to an additional crack bond process with a fresh interface of virgin base metal. The average thickness is reduced from 10 to 5 mu m. The reaction products, CuAl2, CuAl, and Cu9Al4, are dispersed along the rolling direction. Peeling and bending test results indicate that the fracture occurs in the aluminum substrate, and the morphology is a dimple pattern. No crack or separation is found at the bonding interface after 90 degrees-180 degrees bending. The presented method provides an economical way to fabricate Cu/Al clad strip directly.