EBSD study of angular deviations from the Goss component in grain-oriented electrical steels.
The magnetic properties of grain-oriented (GO) electrical steels strongly depend on the distribution of the α and β angles, i.e., the deviations of the easy magnetisation <100> from the rolling direction (RD) in the rolling plane and out of the rolling plane, respectively. However, most Electron Backscatter Diffraction (EBSD) studies consider the standard Goss deviation angle, which includes the rotation of the (110) plane about the RD. Therefore, in the present work, a new procedure is demonstrated for deriving the α and β angles from EBSD mappings to obtain a quantitative texture characterisation in line with the magnetic properties. This procedure is later applied to 37 GO steels after secondary recrystallisation that exhibit a wide range of permeability levels. The relation between the texture and the polarisation at 800A/m (J800) that is measured in the present study by EBSD is compared to the one that has been determined in previous papers with optical goniometers and X-ray diffraction techniques, and this relation is subsequently used to define a relevant parameter to describe the orientation quality of the grains. The results indicate that the average angle of the α and β deviations is a relevant deviation parameter for the characterisation of grain orientations. Finally, it is demonstrated that the combination of the quantitative correlation between polarisation and texture with the orientation imaging of EBSD offers the possibilities of both studying the crystallographic environment of highly oriented grains in the primary recrystallised matrix for the production of high-permeability steels and evaluating the spatial distribution of the angular deviations in GO steels after secondary recrystallisation.
An investigation on the role of texture evolution and ordered phase transition in soft magnetic properties of Fe-6.5 wt%Si electrical steel
Abstract Fe–6.5 wt%Si electrical steel characterized with excellent soft magnetic properties such as almost zero magnetostriction, low eddy current and hysteresis losses characteristics has been widely applied in high frequency fields. In this work, the role of texture evolution and ordered phase transition in soft magnetic properties of annealed sheets was explored using EBSD, XRD and TEM. The results demonstrate that accompanied with the increase of annealing temperatures, an increase on the B8 is attributable to a contribution combining the sizes of recrystallization grains with APBs of ordered phases as pinning the migration of magnetic domain wall. Whereas B50 declines to a minimum value (1.479 T) and then increases to a certain value (1.695 T) due to different types and intensities of textures affecting on the magnetocrystalline anisotropy energy. Meanwhile, the dislocation density gradually decreases and corresponding to a gradual decline in the internal stress, which makes the coercive force (H c ) decrease monotonically.
Influence of subsurface layers on texture and microstructure development in RGO electrical steel
Abstract RGO (regular grain oriented) electrical steel is produced by a two stage cold rolling process with intermediate annealing. In this study the influence of surface layers on the recrystallization behaviour is investigated. By controlled thinning of the sheets at different processing stages surface layers were removed single- and double-sidedly in successive steps of 1/10th of half thickness keeping the final thickness, as well as the 2nd cold reduction, constant. All specimens were processed to the final product relating to standard conditions and texture analysis as well as magnetic measurements being performed, indicating very sensitively any disturbance in Goss-texture development. A deterioration of Goss-texture sharpness only appears if a critical surface layer is removed from both sides of the sheet, no matter the processing stage at which the removal was performed. This result suggests a kind of “texture inheritance” due to a texture profile being present at hot strip with a strong Goss-texture at its surface layer. The observed detrimental effect on secondary recrystallization due to the surface removal can be explained by the texture and microstructure development during the processing of RGO electrical steel. Thus the complete texture and microstructure development was investigated first and explained relating to theoretical models of texture development during deformation and leading to a new understanding of what was called “texture inheritance”.