An attempt was made to determine whether doped and undoped grain boundaries could be distinguished by their response to dislocation pile-ups. The  in situ  straining of foils in a transmission electron microscope showed that dislocations piled up at the grain boundaries, and that slip was transferred across the boundaries ahead of the pile-ups; regardless of whether the alloy contained B or not. It was noted that cracks always propagated along the slip bands, and never along the grain boundaries. This feature was suggested to be a result of a low tensile stress triaxiality in the thin foils.

Y.Xu, E.M.Schulson: Scripta Metallurgica et Materialia, 1995, 33[6], 931-8