Assessing the influence of crystallographic orientation, stress and local deformation on magnetic domains using electron backscatter diffraction and forescatter electron imaging.

The magnetic properties of non-oriented electrical steel (NOES) used in an electrical engine play an important role in the transformation process from electric to mechanic energy. In this process the NOES is subjected to cyclic loading and strong tensile forces. Until now the dependence of the magnetic properties with respect to a through stress changing microstructure is not fully understood. In this paper a setup for a quasi-static in situ deformation experiment with a SEM is presented in which the surface magnetic domains of a NOES were captured by revealing type 2 magnetic contrast with forescatter diodes, the crystallographic texture was mapped through EBSD and the local relative strains and rotations were calculated with CrossCourt. The magnetic domains were related to the angles between the easy axes and the surface as well as the angle differences between the easy axes of neighboring grains. For small differences wide boundary-crossing domain patterns occurred. In contrast, for high ones predominantly compensating domains emerged. Thus a distinct influence of neighboring grains was present. Reaching a certain stress level, a strong tendency of domain alignment along the easy axes closest to the stress direction could be observed. Locally exceeding the elastic limit, slip lines appeared but had no visible influence on the domains. After unloading, in those areas a clear hindrance of domain alignment was apparent, which was attributed to the dislocation accumulations. CrossCourt enables the estimation of GND accumulations, which can be used to detect domain wall pinning. In conclusion, the presented method provides a way to link the magnetic properties of NOES to the texture and a through stress changing microstructure.