Theoretical models were suggested which described the transformation of grain boundaries in nanocrystalline material under plastic deformation. Transformations such as the decay of low-angle boundaries, the bowing of high-angle boundaries and the emission of partial dislocations by boundaries in deformed nanocrystalline material were considered. Within the framework of the suggested model, lattice dislocations that formed a low-angle tilt boundary glided under the action of the forces due to external and internal stresses. The balance of the forces produced the critical shear stress at which the low-angle boundary decayed. Such decay processes resulted in the formation of high-density ensembles of mobile lattice dislocations that were capable of inducing plastic flow localization (shear banding) in mechanically loaded nanocrystalline material. High-angle boundaries were modeled as those containing dislocations with small Burgers vectors. The movement of grain-boundary dislocations under shear stresses gave rise to the bowing of high-angle boundaries. Under certain conditions, the grain-boundary dislocations underwent splitting transformations; followed by the emission of partial dislocations from high-angle boundaries and into adjacent grain interiors. The models accounted for reported experimental data.

Transformations of Grain Boundaries in Deformed Nanocrystalline Materials. S.V.Bobylev, M.Y.Gutkin, I.A.Ovidko: Acta Materialia, 2004, 52[13], 3793-805