Recrystallization texture and microstructure formation in heavily rolled if steel

Abstract

This paper explains how the desirable ∼{111}<hkl> texture of high intensity forms and an undesirable orientation component near {411}<hkl> arises in heavily rolled IF steel. A commercial grade material was warm rolled 75% cold rolled 80% and annealed in a pre-heated air furnace at 710°C. The X-ray measured global texture showed the intensity of a fibre was stronger than γ fibre. During annealing this was replaced by a discontinuous and peak type y fibre. The maximum intensity spread from {554}<225> to {111}<123> which was accompanied by a weaker a component at {411}<148>. The longitudinal and rolling plane microstructure of the deformed material showed that α and γ fibre grains maintain their typical microstructural appearance i.e. the a grains with coarse substructure and the y grains with fine fragmented substructure. The a grains, which are relatively uniform in terms of orientation at lower reductions, became unstable after cold rolling and produced deformation boundaries of the same nature as in y grains. These behaviors can be explained by the well-known Deformation Banding theory for BCC metals. The deformation banding in a grains produce recrystallized nuclei of {411}<uvw> orientation and can be explained by either oriented nucleation or micro-growth selection for the particular orientation belonging to the α fibre. The high intensity spread from {554}<225> to {111}<123> component in the annealing texture is explained by nucleation at the intersection of two sets of in-grain shear bands, but such configuration are rare in conventionally cold rolled material up to 85% reduction.