Microstructure of accumulative roll bonded high purity aluminium laminates

Aluminium sheets of high purity were produced by accumulative roll bonding (ARB) at room temperature. The microstructure of the sheets up to 16 ARB cycles was analyzed by scanning electron microscopy. In all sheets discontinuous dynamic recrystallization occurred leading to coarse grains. In general, the grain size decreases with increasing number of applied ARB cycles, but remains much larger than the theoretical layer thickness after 6 or more ARB cycles. It is shown for the first time, how the interfaces introduced by ARB have a significant effect on the elongated grain shape by a combined experimental-numerical-study: The resulting microstructure is qualitatively discussed with regard to defects introduced at the interfaces by the ARB process, while two-dimensional Potts model simulations yield very good qualitative agreements with the experiments and underpin the importance of the ARB interfaces as barriers for the motion of grain boundaries.