The combined effect of B2 phase transfer and grain boundary character on mechanical properties of the Fe–6.5 wt% Si alloy was investigated. The microstructures and textures of the Fe–6.5 wt% Si alloy under four cooling modes were characterized by X-ray diffraction, transmission electron microscope, and electron backscattered diffraction. The results reveal that the maximum nano-hardness value (8.9 GPa) results from the two-step air-cooling sample, while for the two-step water-cooling sample, the minimum value (5.3 GPa) is achieved. The transformation of the B2 phase affected by the water-cooling process is a critical factor in obtaining the lower APB energy and eliminating the brittlenes. A large fraction of the coincidence site lattice boundaries that formed on the sheet experienced the two-step water-cooling process due to a uniform and sharp γ-fiber recrystallization texture comprising the {111} 〈110〉 and {111} 〈112〉 components, which enhances resistance to intercrystalline effect and improves mechanical properties in comparison with the two-step air-cooling process.

Ordered phases and ductility of Fe–6.5 wt% Si magnetic material were investigated under different rolling temperatures, and the constitutive equation of the warm deformation was established. The results show that at high rolling temperature, accompanying with the appearance of some shallow dimples, the intergranular fracture can be transformed into the quasicleavage fracture, which makes the ductility of warm-rolled sheets greatly improved. In the 450–650 °C rolling temperature range, the antiphase domains (APDs) of warm-rolled sheets are cut, the superdislocation density increases greatly with decreasing warm rolling temperatures, resulting in a decrease in APD sizes during warm deformation. Meanwhile, more B2 and DO3 ordered phases occurring in the matrix improve the long range order parameters, thereby significantly reducing ductility of the alloy. The work softening of Fe–6.5 wt% Si alloy is attributed to a contribution combining the sizes of APDs with ordered phases.