Triple junction nanocracks in deformed nanocrystalline materials

A theoretical model is suggested which describes the generation and evolution of nanoscale cracks (nanocracks) at triple junctions of grain boundaries in deformed nanocrystalline materials. In the framework of the model, nanocracks in nanocrystalline materials are nucleated at triple junctions due to accumulation of the dislocation charge, that accompanies grain boundary sliding through triple junctions. The model accounts for experimental observation [Acta Mater. 51 (2003) 387] of triple junction nanocracks in deformed nanocrystalline Ni. With results of the model, the effects of grain boundary diffusion on suppression of nanocrack generation in nanocrystalline materials exhibiting enhanced ductility and superplasticity are discussed.