Investigation on bonding strength of steel/aluminum clad sheet processed by horizontal twin-roll casting, annealing and cold rolling
In this work, a stainless steel/aluminum clad sheet was produced successfully by horizontal twin-roll casting. The interface morphology, element distribution and bonding strength of the clad sheets after different annealing and cold rolling processes were investigated using optical microscopy, electron probe micro-analyzer and T-type peel test. The surfaces of the steel and aluminum sheets after peeling were studied using scanning electron microscopy. In the as-cast clad sheet, a 3 μm thick diffusional layer exists at the Fe/Al interface. The average peel strength is 12 N/mm. Suitable annealing treatment can greatly improve the bonding quality of the interface. The average peel strength increases with increasing annealing temperature, from 12 N/mm at 450 °C to 21 N/mm at 510 °C. After annealing at 540 °C, the diffusional layer becomes almost three times the original thickness, which results in a sharp drop in the average peel strength to 5 N/mm. Cold rolling processing also improves the bonding strength of the clad sheets. The average peel strength of the clad sheet annealed at 510 °C increases as the reduction in thickness by cold rolling increases, from 23 N/mm for 25% reduction, to 28 N/mm for 40% reduction.