Shear band formation in warm rolled IF steel

Abstract

When IF steel is rolled to 75% reduction in a single pass at elevated temperatures within the ferrite phase, the rolling texture consists of the α and γ fibres. The microstructure revealed by Scanning Electron Microscopy (SEM) shows the γ fibre grains to be composed of microbands (MBs), while the α fibre grains have a coarse smooth structure. In addition to this, extremely fine grain scale shear bands (SBs) appear which cut through the microbands in the γ fibre grains but are not present in α fibre grains. The material inside the shear bands has ∼8-10° misorientation with the neighboring matrix and the rotation axis between shear band and the matrix material is not fixed to any of the samples reference directions. A model for shear band formation is proposed based on crystallographic slip system. Both {110} and {112} slip planes were considered to find the operative slip systems. The modeled shear band material rotates around the normal direction to the shear direction on the operative slip planes. Some experimental evidence, derived from SEM and OIM, supports this prediction.