Disclination dipoles observation and nanocrystallization mechanism in ball milled Cu–Nb powders

Abstract

The object of this work is 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 is directly revealed to be constituted by individual dislocations. It is found that such disclination defects can 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.