Investigation on the Strain Induced Oxide Layer Fracture and Bonding During Cold Rolling of Aluminum Alloys

Physical bond rolling experiments of aluminum sheets have been investigated in this study. In addition to native oxides on surface of aluminum, a thick oxide layer was deliberately added to AA3xxx aluminum sheets by anodization. For better monitoring of evolution of the oxide layer during roll bonding, the anodized layer was colored with Indigo Carmine in the anodization process. A progressive reduction per pass ranging from 2 to 70% has been performed in consecutive experiments at a constant rolling speed to develop different degrees of oxide surface expansion leading to its fracture and leaving disparate oxide fragments. The evolution of the oxide fragmentation and bonding of aluminum sheets were systematically characterized as a function of deformation by electron microscopy. It was revealed that the crack width between fragmented oxides increases exponentially while the oxide fragment size decreases exponentially as a function of the reduction ratio.