In-situ visualization of stress-dependent bulk magnetic domain formation by neutron grating interferometry
The efficiency of industrial transformers is directly influenced by the magnetic properties of high-permeability steel laminations (HPSLs). These laminations are coated by insulating layers, to reduce eddy-current losses in the transformer core. In addition, the coating induces favorable inter-granular tensile stresses that significantly influence the underlying magnetic domain structure.
In this work, we show how the neutron dark-field image can be used to analyze the influence of the coating on the volume and supplementary surface domain structures. For the visualization of the stress effect of the coating on the underlying domain formation, we used an uncoated HPSL and stepwise increased the applied external tensile stress up to 20 MPa. We imaged the domain configuration of the intermediate stress states and we were able to reproduce the original domain structure of the coated state. Furthermore, it is shown, how the applied stresses lead to a refinement of the volume domain structure and the suppression and reoccurrence of supplementary lance-leaf domains.
In this work, we show how the neutron dark-field image can be used to analyze the influence of the coating on the volume and supplementary surface domain structures. For the visualization of the stress effect of the coating on the underlying domain formation, we used an uncoated HPSL and stepwise increased the applied external tensile stress up to 20 MPa. We imaged the domain configuration of the intermediate stress states and we were able to reproduce the original domain structure of the coated state. Furthermore, it is shown, how the applied stresses lead to a refinement of the volume domain structure and the suppression and reoccurrence of supplementary lance-leaf domains.