In-situ observation of plastic deformation of Fe-Si bicrystals by white-beam synchrotron radiation topography

In-situ experiments using synchrotron X-ray topography have been carried out in order to study dislocation transmission through grain boundaries in bicrystals of Fe-4 at.% Si alloy in the initial stage of plastic deformation. The grain boundaries hinder dislocation motion even in case of the most favourable slip geometry, that is when both Burgers vectors and slip planes are parallel in the two grains. The slip transmission is greatly affected by the stresses exerted by dislocations stopped at the grain boundaries and by the local structure of the grain boundary itself. The slip behind the boundary starts most probably from new dislocation sources formed under combined external and internal stresses.