A relay-race dislocation-disclination model of plastic shear development in nanocrystalline materials was proposed, which was based upon the mechanism of switching between translational and rotational deformation modes. The dependence of the external deforming stress on the grain size was calculated. It was shown that the switching from the translational to rotational deformation mode and back explained the reverse Hall-Petch effect in nanocrystalline materials.

Dislocation-Disclination Transformations and the Reverse Hall-Petch Effect in Nanocrystalline Materials. A.L.Kolesnikova, I.A.Ovidko, A.E.Romanov: Technical Physics Letters, 2007, 33[8], 641-4