An investigation into the formation of microbands and shear bands in IF steel

Abstract

Microbands form at rolling strains of ∼10% in IF steels and are of lenticular shape. Transmission electron microscopy shows that the dislocation walls are parallel to 110 and 112 planes. The shear fraction on each active slip system and the Taylor factors have been determined for various orientations. The results show that when shear is heavily concentrated on one slip plane, microbands are formed. The angle between the rolling direction and the trace of the active slip plane is about 30° for crystals with <110> and <111> parallel to TD and this angle ensures a high shear on the slip plane. At rolling reductions greater than 50% shear bands appear in the microstructure, and these are shown to involve the same slip systems as the microbands. The microstructure indicates that shear banding involves rigid body rotations and dislocation glide.