Effects of twins on deformation and recrystallization behaviors in the preparation of ultrathin grain-oriented electrical steel

When preparing ultrathin grain-oriented electrical steel using commercial grain-oriented electrical steel strip as the starting material, an abundance of deformation twins is observed in initial dominant Goss oriented grains. In this study, the evolution and effect of these twins are focused in terms of both crystallographic orientation and local strain and, based on this study, to explore their influence on recrystallization microstructure and texture evolution. Results show that in 0.075 mm ultrathin grain-oriented electrical steel, the differences in the twin distribution characteristics are common between Goss oriented grains of different accuracies as well as inside individual coarse grains. A high percentage of twins meet and promote each other at grain boundaries, reflecting the role of more localized stress-strain concentration. The twin orientation becomes increasingly diffuse at higher rolling reduction, but the majority deviates from ideal {001}<110> orientation by < 15°. The local strain gradient at the twin boundary increases, but this increase is progressively reduced as the rolling reduction increases. In terms of crystallographic orientation, the retention of Goss orientation is promoted in the regions close to the twin boundary, while the proportion of {111}<112> oriented regions is slightly reduced. After annealing, the nuclei at the twin boundaries do not show advantage in both size and quantity compared to the nuclei at the shear bands and deformation induced grain boundaries, meanwhile Goss orientation does not show advantage in all nuclei. The twins are retardation regions in the recrystallization process, but have no significant effect on microstructure inhomogeneity.