Characterization of ordering in Fe-6.5%Si alloy using X-ray, TEM, and magnetic TGA methods

Ouyang, Gaoyuan
Jensen, Brandt
Macziewski, Chad
Ma, Tao
Meng, Fanqiang
Lin, Qishen
Zhou, Lin
Kramer, Matthew
Cui, Jun
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Ames Laboratory
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Fe-6.5wt%Si steel surpasses the current extensively used Fe-3.2wt%Si steel in lower iron loss, higher permeability, and near zero magnetostriction. As a cost effective soft magnetic material, Fe-6.5wt%Si may find applications in motors, transformers, and electronic components. However, the brittleness of the alloy poses processing challenges. The brittleness in Fe-6.5wt%Si is attributed to the formation of ordered phases. Evaluation of the amount of ordered phases is important for the research and development of Fe-6.5wt%Si. This paper aims to find effective ways to evaluate the ordering degree through a comparison of various characterization techniques. In order to tune the ordering degree, various speeds were used to prepare Fe-6.5wt%Si samples via melt spinning. The varying wheel speed changes the cooling rate, which was confirmed by thermal imaging. In addition to the widely used TEM and normal theta-2theta X-ray diffraction methods, two quantitative methods were adopted for this Fe-6.5wt%Si system to study the ordering degree. One method is based on rotating crystal XRD technique, and the other is magnetic thermal analysis technique. These two methods effectively quantified the varying degree of ordering presented in the samples and were deemed more suitable than the TEM, normal theta-2theta XRD methods for Fe-Si due to their ease of sample preparation and short turn-around time.

Silicon steel, Ordering, Melt spinning, Transmission electron microscopy, Magnetic thermal gravimetric analysis