Formation mechanism and microstructure of a forsterite film in grain-oriented electrical steel

Abstract

Grain-oriented (GO) electrical steel is widely used as electrical and magnetic engineering materials and its core loss is required to be as low as possible. An effective way to reduce the core loss of iron is to apply tensile stress to GO electrical steel. A method to form an Mg2SiO4 (forsterite) film with a lower thermal expansion coefficient on the surface of GO electrical steel has been commonly used for the application of tension to the steel. In this article, the formation mechanism of a forsterite film changed from a decarburized oxide layer on GO electrical steel surface through the process of the secondary recrystallization annealing is studied. Additionally, it is reported that intermediate compositions have been generated in the reaction process at each temperature range during annealing. For the investigation of the forsterite formation mechanism, such several characterization methods as X-Ray Diffraction, Scanning Electron Microscopy, and transmission electron microscopy with energy dispersive X-ray spectroscopy were employed.