Microbands are well-known deformation features that generate in the rolling microstructures of many metals and alloys. The boundaries across two neighbouring microbands are comprised of dense dislocation walls and they accommodate a small average crystallographic rotation in the range of 1-4°. In this study, a combination of high resolution electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) was used to observe orientation differences of up to 20° across microband boundaries in the rolling substructures of {111}<110> oriented grains in steel. Despite their high angle nature, the microband interfaces maintain their well-known crystallographic characteristics, by being closely aligned with highly stressed slip planes. Rigid body rotations are argued to take place around the interface normal between adjacent microband lattices. This results in an unusual microstructure whereby alternating microband boundaries, oriented in equal and opposite relative angles, produce an array of orientation pairs in their spatial distributions.
A focused ion beam (FIB) coupled with high resolution electron backscatter diffraction (EBSD) has emerged as a useful tool for generating crystallographic information in reasonably large volumes of microstructure. In principle, data generation is reasonably straightforward whereby the FIB is used as a high precision serial sectioning device for generating consecutive milled surfaces suitable for mapping by EBSD. The successive EBSD maps generated by serial sectioning are combined using various post-processing methods to generate crystallographic volumes of the microstructure. This paper provides an overview of the use of 3D-EBSD in the study of various phenomena associated with thermomechanical processing of both crystalline and semi-crystalline alloys and includes investigations on the crystallographic nature of microbands, void formation at particles, phase redistribution during plastic forming, and nucleation of recrystallization within various regions of the deformation microstructure.
A focused ion beam (FIB) coupled with high resolution electron backscatter diffraction (EBSD) has emerged as a useful tool for generating crystallographic information in reasonably large volumes of microstructure. In principle, data generation is reasonably straightforward whereby the FIB is used as a high precision serial sectioning device for generating consecutive milled surfaces suitable for mapping by EBSD. However, there are several challenges facing the technique including the need for accurate reconstruction of the EBSD slice data and the development of methods for representing the myriad microstructural features of interest including, for example, orientation gradients arising from plastic deformation through to the structure of grains and their interfaces in both single-phase and multi-phase materials. This paper provides an overview of the use of 3D-EBSD in the study of texture development in alloys during deformation and annealing and includes an update on current research on the crystallographic nature of microbands in some body centred and face centred cubic alloys and the nucleation and growth of grains in an extra low carbon steel.
The crystallographic alignment of microbands in a Goss oriented single crystal was investigated by two and three dimensional electron back scatter diffraction. The microband boundaries were found to be curved instead of being perfectly flat interfaces, and the overall alignment closely matched a potential slip plane. The bumps and curved were created during subsequent deformation and, thus, deviates the microband boundaries from crystallographic nature.
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