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A theoretical model is suggested which describes structural and
behavioral features of grain boundary dislocation configurations near triple
junctions in nano- and polycrystalline materials. With the elastic interaction
between grain boundary dislocations taken into account, we have theoretically
examined deviations of spatial arrangement of boundary dislocations near triple
junctions, from a periodic arrangement. Also, the local migration of grain
boundaries near their triple junctions has been theoretically described, induced
by grain boundary sliding in mechanically loaded nano- and polycrystalline
materials. In the framework of the model, the key driving force for the local
migration is a release of the elastic energy of ensemble of gliding boundary
dislocations (carriers of grain boundary sliding) and immobile boundary
dislocations (associated with grain boundary misorientation). It is shown that
migration is capable of effectively enhancing grain boundary sliding, in which
case the combined effects of grain boundary sliding and migration near triple
junctions cause plastic flow localization in fine-grained materials, reported in
the literature.
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