Shear band formation in warm rolled IF steel

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 alpha and gamma fibres. The microstructure revealed by Scanning Electron Microscopy (SEM) shows the gamma fibre grains to be composed of microbands (MBs), while the a 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 gamma fibre grains but are not present in alpha fibre grains. The material inside the shear bands has similar to8-10degrees 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 I I 101 and 11121 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.