Microstructural Origin of Magnetic Properties in Grain-Oriented Silicon Steel: Shear Band Angle Control of Intraband Lattice Rotation

The magnetic properties of grain-oriented silicon steel depend on the sharpness of its Goss texture, which is governed by the density of Goss areas formed in cold-rolling shear bands. This density rises with the intraband lattice rotation rate ω, which is governed by the shear band angle θ through the local shear strain tensor. Reported relationships between θ and the intraband Goss density are inconsistent, and how θ influences ω remains unclear. Slip geometry analysis, crystal plasticity calculations and quasi-in situ electron backscatter diffraction (EBSD) were combined to investigate an Fe-3.0 wt.% Si alloy. The results show that the intraband orientation evolution is retarded by the primary slip system (112)[ ̅1 ̅11], most strongly at the retardation plane Φr = 35.3° + θ. The {111} matrix accordingly divides into locked, escaped and free regions, depending on whether the orientation reaches the <110>//ND fiber within a finite strain. As θ falls from 35° to 17°, ω of the escaped region rises. Quasi-in situ tracking supported the increase in ω as θ decreases. Despite a smaller shear strain (2.82 vs 3.63), the θ = 25° band crossed the <110>//ND fiber, whereas the θ = 30° band had not yet reached the fiber. θ alters both the slip system activity at the retardation plane and where the orientation crosses it. These results provide a crystallographic basis for controlling intraband Goss density.