| A theoretical model is suggested which describes stress-induced nucleation of nanoscale grains (nanograins) in deformed nanocrystalline metals and ceramics as a process occurring through splitting and migration of grain boundaries. In the framework of the model, nucleation of nanograins is initiated by deformation modes (intergrain sliding, lattice slip, twin deformation, stress-driven migration of grain boundaries) that create disclination dipoles at grain boundaries. The nanograin nucleation occurs through splitting and migration of grain boundaries containing disclination dipoles. It is shown that the nanograin nucleation is energetically favorable in mechanically loaded nanocrystalline Al and α-Al2O3 in certain ranges of their parameters and the external stress level. |
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