Magnetic domain structure and crystallographic orientation of electrical steels revealed by a forescatter detector and electron backscatter diffraction

Matthew Gallaugher; Nicolas Brodusch; Raynald Gauvin; Richard R Chromik

doi:10.1016/j.ultramic.2014.03.013

Magnetic domain structure and crystallographic orientation of electrical steels revealed by a forescatter detector and electron backscatter diffraction

Ultramicroscopy. 2014 Jul:142:40-9. doi: 10.1016/j.ultramic.2014.03.013. Epub 2014 Apr 13.

Authors

Matthew Gallaugher¹, Nicolas Brodusch¹, Raynald Gauvin¹, Richard R Chromik²

Affiliations

¹ McGill University, Department of Mining and Materials Engineering, 3610 University Street, Montreal, Quebec, Canada H3A 0C5.
² McGill University, Department of Mining and Materials Engineering, 3610 University Street, Montreal, Quebec, Canada H3A 0C5. Electronic address: richard.chromik@mcgill.ca.

PMID: 24769020
DOI: 10.1016/j.ultramic.2014.03.013

Abstract

The magnetic properties of non-oriented electrical steels (NOES) are an important factor in determining the efficiency of electric vehicle drivetrains. Due to the highly variable texture of NOES, the relationships between crystal orientation, the magnetic domain structure, and the final magnetic properties are complicated and not fully understood. In this study, a NOES sample was characterized with a method capable of imaging surface magnetic domains using scanning electron microscopy (SEM) with an electron backscatter diffraction (EBSD) system equipped with a forescatter detector. This method used type II magnetic contrast without a specialized SEM setup, and imaged with a resolution limit of approximately 250-300nm. The domain structure of the NOES sample was successfully related to β, which was defined as the angle between the closest magnetic easy axis and the surface of the sample (the RD-TD plane). However, it was shown that if the easy axes were aligned between neighbouring grains with respect to the grain boundary normal, the domain structure could align with an easy axis that was not the closest to the surface, and complex domain structures could be become wider. This structure and width change of complex domain structures has not been previously observed from single crystal or large-grained material studies. The successful application of this method to reveal the influence of surrounding grains can be used to better understand the magnetic properties of NOES.

Keywords: Electron backscatter diffraction (EBSD); Forescatter detector (FSD); Magnetic domains; Magnetic free pole density; Non-oriented electrical steels (NOES); Scanning electron microscopy (SEM); Texture; Type II magnetic contrast.

Publication types

Research Support, Non-U.S. Gov't