Deformation banding and recrystallization of α fibre components in heavily rolled IF steel

Detailed SEM work has shown that about a quarter of crystals belonging to the a fibre formed by cold rolling up to reductions of 85%, are of uniform microstructure with relatively small misorientation. The remainder are indistinguishable from the polycrystalline mass, which is mostly of gamma orientations. At rolling reductions above 85%, alpha grains begin to split their orientations by deformation banding. thus producing lattice curvature which allows recrystallization of alpha at the expense of other alpha components in the same original grain. This alpha recrystallization deteriorates the deep drawability of IF steel and since the process requires deformation banding a natural explanation of the optimum rolling reduction for good drawability is provided. The best cold rolling reduction is that which optimizes gamma recrystallization by producing deformation banding in gamma components without producing deformation banding in alpha components. Uniform microstructures and small lattice curvature allows alpha to be consumed by other orientations, and this condition is obtained in the 80-85% cold rolling range. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.