Formation of Intermetallic Compounds in Al–Cu Interface via Cold Roll Bonding: Review

The composites consisting of similar or dissimilar metallic layers with different physical properties are vastly applicable. Among various methods for producing these composites, cold roll bonding (CRB) is considered to be more efficient and more cost-effective than other bonding processes. Nowadays, Al-Cu layer composite bonds are favorable in different industries due to their low price, well conductibility, high corrosion resistance, high deformation, and good electrical conduction. This review paper deals with the investigations of the Al-Cu cold rolling process, of the bonding mechanism of metallic layers during CRB, and of the effect of the roll bond strength parameters such as initial thickness, for one. Roll bonding has three levels: (1) physical touch; (2) activating surfaces in touch; (3) interaction between bonding metals. CRB is supposed to be an in-plane strain, and the normal stress distributed on the top and bottom rollers is homogeneous. Annealing before and after rolling, the direction and speed of rolling, the amount of thickness reduction, and the lubrication conditions on the Al–Cu bond through the roll bonding process were studied. The effect of different annealing conditions on the produced intermetallic compounds at the Al–Cu rolling bond interface and the growth of the intermetallic phases and their impact on the CRB parameters was examined. The thickness of intermetallic compounds, thickness reduction under the rolling process, the rolling speed, the annealing temperature, and time affected the bond strength. The effect of the rolling speed on the bond strength depends on the touching time between the sheets during rolling, which means that the touching time between two surfaces of Al and Cu sheets reduces at higher rolling speeds. As a result, the chance for proper bonding is lost, and, therefore, the bond strength is decreased.