The migration of <110> tilt boundaries in Fe-Si bicrystals was investigated as a function of misorientation angle, driving force, temperature and Si content. Two distinct regimes, with differing migration behavior, were observed in the temperature dependence of the mobility. A sharp change in mobility occurred at a critical temperature. The latter temperature depended upon the driving force and upon the nature of the grain boundary. The activation energy for grain boundary migration was equal to about 2/3 of that for Fe bulk self-diffusion in the higher-temperature region; thus suggesting that the boundary motion was governed by grain boundary diffusion. On the other hand, the activation energy increased up to about 220kJ/mol in the lower-temperature regime, and agreed with that for Si intrinsic diffusion in a-Fe. This agreement showed that the grain boundary was most likely to move while dragging a Si atmosphere. It was also of great interest that the mobility of the coincidence boundary, particularly S9, was higher than that for a random boundary in the lower temperature regime, while the opposite was true in the higher-temperature regime. Moreover, the mobility depended upon the Si content in the lower-temperature regime. It increased with decreasing Si content, whereas no such dependence was clearly observed in the higher-temperature regime.

Grain Boundary Migration in Fe-Si Alloy Bicrystals. S.Tsurekawa, H.Nakashima: Materials Science Forum, 1999, 294-296, 629-32