Mechanism of warm and cold roll bonding of aluminum alloy strips

From a study of interfacial behavior at deformations up to 60%, a mechanism is proposed for pressure welding of aluminum strips by rolling at warm and cold conditions, where faying surfaces were first degreased and scratch-brushed. According to this mechanism, the scratch-brushed layers fractured coherently after entering roll gap at a reduction of approximately 21%, which is regarding to the threshold deformation for roll bonding of commercial pure (CP) aluminum strips, and some small cracks perpendicular to the rolling direction formed. As deformation proceeds and roll pressure increases, these cracks quickly expanded into fissures. This process allowed the bond to be established between the underlying metals, termed virgin metals, of base metal, which were extruded through the cracks and fissures at the scratch-brushed regions. Moreover by increasing the rolling temperature, threshold deformation required for bond formation decreases.