Unusual Crystallographic Aspects of Microband Boundaries within {111}^|^lt;110^|^gt; Oriented Grains in a Cold Rolled Interstitial Free Steel

Abstract

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.

Grain Boundary Deformation Phenomena and Secondary Growth of Goss Grains in a Fe-3.5%Si Steel

“…23,27) Also, the misorientation across these lines are less than 0.8° and therefore these features are not considered to be microbands, because typical microbands accommodate misorientations of at least few degrees 28,29) which in some exceptional cases can be as high as ~18°. 30) It is obvious from the STEM and TEM images, in Figs. 3 and 4, that the MnS particles provide the pinning effect to the boundaries, and therefore, the growth takes place after their dissolution at 900-1 000°C temperatures.…”

Patterns of Grain Fragmentation During Plastic Deformation of Metals at Small to Medium Strains (Brief Review)

“…A special kind of microbands was observed to form in cold-rolled interstitial free steel, in grains with orientations near {111}<110> [48], as well as in tensile strained iron with the development of <110> fiber texture [49,50]. Bands of this kind cannot be attributed to "secondary bands", strictly speaking, since their alignment and internal substructure coincide with those of primary bands.…”