Effects of topology on abnormal grain growth in silicon steel

This work addresses the role of grain topology on abnormal grain growth in silicon steel. The question was investigated whether the abnormal grain growth of Goss grains during secondary recrystallization can be interpreted in terms of an initial size advantage that these grains inherit from rolling and primary recrystallization. For this purpose the correlation between crystallographic orientation, size and number of next neighbors of large grains in the subsurface layer of a primary recrystallized silicon steel sheet was investigated. It was found that most of the large grains have an orientation on the h-fiber ( 001 axis parallel to the rolling direction) but are not particularly close to the Goss orientation. Also, no tendency of grains to be larger the closer they are to the Goss orientation was visible. Rather it was found that the scatter of the angular deviation to the Goss orientation is similar over a large range of grain sizes and this was found to be true too if the number of next neighbors of a grain rather than its grain size was checked. One single grain, however, was found that was close to the Goss orientation and had a high number of next neighbors and might therefore act as a nucleus for secondary recrystallization. Nevertheless, grains with a similarly high number of neighbors and a large deviation to the Goss orientation were found, too. Thus, a topological reason for the Goss texture evolution could not yet be proved. However, it might be that the extreme rareness of Goss nuclei (1 out of 10 6 grains) has prevented, up to now, from observing a true nucleus.