Influence of cross-rolling on the mechanical properties of an accumulative roll bonded aluminum alloy AA6014

Sheets of aluminum AA6014 (AlMgSi) were successfully accumulative roll bonded from T4 condition up to eight cycles. Using the conventional ARB route, processing was on the one hand performed at room temperature. On the other hand, sheets were pre-heated in a furnace for 2.5 min at 210 °C prior to each rolling step. Besides the conventional ARB route an ARB cross-rolling route, where the rolling direction is rotated around 90° after each cycle, was used at room temperature. For all three processing conditions an ultrafine-grained microstructure was obtained. Due to a change in strain path, the ultimate tensile strength and the yield strength of the cross-rolled AA6014 exceed those of the samples processed by conventional ARB. However, a strong decrease in terms of elongation to failure is visible after 6-8 cycles of ARB compared to the pre-heated ARB sheets. Fracture analysis reveals necking of individual layers for the samples processed at room temperature. Therefore, after 7 cycles of cross-rolling at RT, one last cross-rolling step at elevated temperature was performed in order to improve bonding quality. This leads to a high strength of about 475 MPa and a satisfactory elongation to failure of about 10%.