Article ID: TETSU-2024-104
Two orientations ({110}<001> and {110}<112>) evolve as secondary grains in heavily cold rolled reduction of 91.5% in grain-oriented silicon steel. We investigated the secondary recrystallization mechanism of these two grains by temperature gradient batch annealing method. This method induces the continuous growth of secondary grains along the temperature gradient direction. Consequently, selective growth behavior can be easily evaluated from macrostructure. Furthermore, the orientation relationships between secondary recrystallized grains and primary recrystallized grains at the interface of them can be investigated by interrupting the temperature gradient batch annealing process during the secondary recrystallization. It was clarified that secondary grains which have higher frequency of CSL (Coincidence Site Lattice) boundaries grow more preferentially and the effective CSL boundaries tolerance angle was 10 degrees from precise CSL orientations. Both {110}<001> and {110}<112> grains statistically had a high frequency of effective CSL boundaries (more than 14.5%) and CSL boundaries corresponding to each orientation of secondary grains disappeared preferentially at growing fronts of each secondary grain. It can be deduced that CSL boundaries dominate the selective growth behavior of {110}<001> and {110}<112> grains, which have two or more neighboring CSL boundaries to the matrix and thus successively grow as secondary grains. CSL boundaries are supposed to have lower grain boundary energy and higher mobility. Therefore, CSL boundaries suffer lower pinning forces from inhibitors and start to migrate from higher inhibition level (lower temperature). From these results, CSL boundaries play a dominant role in the secondary recrystallization of heavily cold rolled grain-oriented silicon steel.
