Surface roughness – the key for roll bonding aluminium

Abstract

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.

Friction Stir Welding (FSW): Solid-State Joining of Composite Materials

“…• Adhesive and abrasive wear behaviors are observed, with the weld zone generally exhibiting superior wear resistance compared to base composites [39][40][41].…”

New aspects of solid-state welding in the aluminium accumulative roll bonding

“…25 reported that SSW adhesion through rolling increases as the initial roughness of the sheets rises, as confirmed by Biradar and Rijesh. 26 Bay 27,28 confirmed that SSW occurs locally, at the contact of ‘high spots’ in the two surfaces to be joined; in addition, a modified ‘film theory’ was proposed, where the surface cracks before the extrusion would occur through the ‘…fracture of the work hardened surface layer produced by scratch brushing and exposure of the base metal’. This surface layer is denominated ‘cover layer’ and the ‘… fracture of a brittle cover layer’ is mentioned, in the so-called C–C mechanism.…”