Microstructural evolution of twin-roll-cast Al–Mn alloy during cold rolling and subsequent annealing: Effect of number of cold-rolling passes

Variations in the shape and microstructure of a 3003 Al alloy strip fabricated by twin-roll casting during cold rolling and subsequent annealing are investigated as a function of the number of cold-rolling passes under the same total rolling reduction. With an increase in the number of cold-rolling passes, the length and width of the cold-rolled sheet increases and decreases, respectively, owing to a reduction in the ratio of the deformation zone length to the mean deformation-zone thickness. A homogenized twin-roll-cast strip has much coarser grains and more particles in the surface region than in the center region. The shape, amount, and distribution of the particles remain unchanged after cold rolling and subsequent annealing, and they are independent of the number of cold-rolling passes. However, as the number of cold-rolling passes increases, the amount of plastic deformation accumulated in the surface region of the cold-rolled sheet increases. As a result, the size of recrystallized grains in the surface region of the subsequently annealed sheet gradually decreases with increasing number of cold-rolling passes owing to the enhanced recrystallization behavior. Therefore, the grain size difference between the surface region and the center region of the annealed sheet reduces significantly, and the homogeneity of the microstructure in the thickness direction of the sheet improves with an increase in the number of cold-rolling passes.