Surface roughness - the key for roll bonding aluminium

In this study, the commercially pure aluminium is roll bonded at ambient temperatures. The effect of surface roughness and roll speed on the bond strength is evaluated by using the lap shear test. It is observed that the bond strength increased considerably with increasing surface roughness. The deformation caused owing to scratch brushing changed the surface roughness profile, which is the salient reason for the bond strength variation. Continuous striations with peaks and valleys of small-scale heights are observed at lower roughness values. Increasing roughness has reformed them into discrete profile asperities with sharp tips, influencing localised junction formation. On the other hand, the roll velocity has shown hardly any effect on the roll bonding of aluminium. With thorough investigation, it was conclusively explained that the effective change in the bond strength was not appreciable with varying the roll speed, provided the roll bonding takes place at optimised surface roughness conditions.