Institute for Problems of Mechanical Engineering, Russian Academy of Sciences,
Bolshoj 61, Vas. Ostrov, St. Petersburg 199178, Russia
| A theoretical model is suggested which describes the role of grain boundary dislocation climb in high-strain-rate superplastic deformation of nanocrystalline materials. In the framework of the model, grain boundary sliding causes the dislocation storage at triple junctions of grain boundaries in nanocrystalline materials under superplastic deformation. This effect is responsible for strengthening. The dislocation climb along grain boundaries adjacent to dislocated triple junctions provides relaxation of the dislocation charge accumulated at the triple junctions. As a corollary, the grain boundary dislocation climb hampers the nanocrack generation and gives rise to softening of nanocrystalline materials under superplastic deformation. |
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