Papers by Keyword: BCC

Abstract: Orientation microscopy, based on electron backscattered diffraction (EBSD) has been used to study the regularities of formation of the crystallographic texture in materials with BCC and FCC lattices in the hot rolling process throughout the whole thickness of the strips. It has been established that the texture of the central layers of all samples consisted of the discrete sets of stable orientations corresponding to the cold rolling texture. In the surface layers of the samples Fe-3%Si and Al, the texture consisted of sets of discrete orientations corresponding to the shear structure. In the samples of Mo and austenitic steel, the set of discrete orientations of the surface layers matched the texture of the central layers. The difference in textures of the central and surface layers was the result of a certain stress state. The amount of friction has notably influenced the texture of the surface layer. In "hard" materials (Mo, γ-Fe), the friction was minimal, i.e. the difference in stress states of the surface and central layers was insignificant.

Abstract: Atomistic simulations are used to describe the ½<111> screw dislocation in tungsten. Two different embedded atom model (EAM) potentials and one bond-order potential (BOP) are compared. A new analytical approach for constructing asymmetrical screw dislocations is presented.

Abstract: Taylor-type and finite element polycrstal models have been embedded into the commercial finite element code ABAQUS to carry out the crystal plasticity finite element modelling of BCC deformation texture based on rate dependent crystal constitutive equations. Initial orientations measured by EBSD were directly used in crystal plasticity finite element model to simulate the development of rolling texture of IF steel under various reductions. The calculated results are in good agreement with the experimental values. The predicted and measured textures tend to sharper with an increase of reduction, and the texture obtained from the Taylor-type model is much stronger than that by finite element model. The rolling textures calculated with 48 {110}<110>, {112}<111> and {123}<111> slip systems are close to the EBSD results.

Abstract: The presence of hcp regions with grains having relatively close orientations has been reported in commercial near alpha titanium billets (IMI 834, Ti 6246, etc). The size of these textured regions (called macrozones) is significantly larger than the average grain size of the microstructure observed after thermomechanical processing. The elongated shape of these large hcp regions suggests that they are eventually related to large prior b grains that pancaked during the ingot break down process. In this contribution, Orientation Image Microscopy was used to study the relationship between the hcp local microtexture heterogeneities and the prior b orientations. Specifically, the orientations of the primary (equiaxed) ap grains and the secondary (lamellar) as colonies produced after the transformation of the b phase were discriminated from OIM maps. Furthermore, from the as inherited OIM map, it was possible to reconstruct the corresponding b OIM map over large regions. The analysis showed that the large hcp macrozones observed in the as received material are not related to corresponding bcc macrozones. However, within an hcp macrozone, various clusters of b grains with similar orientations can be found. In such coherent regions, randomly orientated b grains were also observed, which could be related to microstructural changes during deformation (continuous dynamic recrystallization) as suggested by hot deformation results.