In-situ transmission electron microscopy observation of slip propagation in Σ3 bicrystals

In-situ straining experiments have been performed to study the mechanisms of propagation of deformation at grain boundaries (GB) in symmetrical Σ3 Fe–4 at.% Si bicrystals with common primary slip system in both grains. Three different orientations of tensile axis with respect to the {112} GB plane were studied and three different effects were observed. In no case was the propagation of primary-slip dislocations across the GB observed. When the tensile axis lies in the GB plane, the slip dislocations of the tertiary slip system enter the GB, interact with GB dislocations, and the dislocations of the secondary slip system are generated in the second grain. When the angle between the primary slip plane and the GB is about 20°, the primary-slip dislocations whose Burgers vectors belong to the GB plane, cross slip and follow the GB plane. Primary-slip dislocations are formed in one grain and a new sub-grain boundary is formed in the other grain when the angle between the primary slip plane and the GB is about 49°.