Microstructure-dependent magnetic properties of iron silicon single, bi- and oligo-crystals measured with a miniaturised Single-Sheet-Tester

Abstract

Electrical steel is the most commonly used soft magnetic material in electrical energy conversion and transmission, and its demand is expected to increase with the need for electrification of the transportation sector and the transition to renewable energy to combat climate change. Although iron silicon steel has been used for more than 100 years, some fundamental relationships between microstructure and magnetic performance remain vague, especially with regard to the role of crystal defects such as grain boundaries and dislocations that are induced during the final cutting step of the process chain. In this paper we present first results of a new approach to quantify the effects of orientation, grain boundaries and deformation on the magnetic properties of single, bi- and oligo-crystals using a miniaturised Single-Sheet-Tester. In this way, we were able to better resolve the orientation-dependent polarisation curves at low field strengths, revealing an additional intersection between the medium and hard axis. Furthermore, we were able to distinguish the effects of different deformation structures – from single dislocations to tangles to localised deformation and twins – on different magnetic properties such as on coercivity, remanence and susceptibility. We also found that our particular grain boundary with predominately 41° (4912¯) misorientation strongly reduces the remanence.