Atomic-scale observation of Σ5{310} and Σ9{411} grain boundaries in silicon steel

Abstract Grain boundaries (GBs) play a significant role in the formation of coarse-grained texture of silicon steels. Recently, an unusual GB atomic structure has been found in Σ9{221} GB in silicon steel, where the structure is incommensurate with the bulk crystal structure and structural fluctuation may be present due to the phason mode of the incommensurate structure. This new finding evokes the necessity of atomic-scale structural analysis of GBs in silicon steel for other orientation GBs. In this study, we characterized the atomic structure of Σ5{310} and Σ9{411} GBs in silicon steel using magnetic-field-free atomic resolution scanning transmission electron microscopy and theoretical calculation. We have revealed that the observed GB structures matched the previous theoretical predictions. We suggest that the low GB excess and the distorted local atomic structures may be the key factors for the formation of incommensurate GB structures.