The object of this work was to investigate the structure of disclination dipoles and the nanocrystallization mechanism in ball-milled Cu–Nb powders. The structure of the partial disclination dipole in the nano-sized, face-centered cubic Cu crystals was directly revealed to be constituted by individual dislocations. It was found that such disclination defects could produce large lattice rotations at the nanometer scale in crystals during milling. The observation of microstructural evolution and analysis of the nanocrystallization mechanism indicate that the grain refinement induced by severe plastic deformation dose not only depend on the actions of dislocations and twins, but also on the disclination defects, especially for the further refinement of nano-size crystals.

Disclination Dipoles Observation and Nanocrystallization Mechanism in Ball Milled Cu–Nb Powders. R.S.Lei, M.P.Wang, Z.Li, H.G.Wei: Materials Letters, 2011, 65[19-20], 3044-6