Both molecular dynamics simulations, and high-resolution transmission electron microscopy observations, had shown that, for nanocrystalline Al, mechanical twinning played an important role in the deformation process. These results were surprising, since partial dislocations in high stacking-fault energy face-centered cubic metals were expected to be unstable. A plausible explanation was offered here for the occurrence of stacking faults and deformation twins in nanocrystalline Al. A simple model was developed for the nucleation of both perfect and partial dislocation half-loops in individual single-crystal nanoparticles of Al and Cu having different sizes when subjected to a shear stress. The model showed that, as the size of the nanoparticles decreased, partial dislocations were more likely to occur. For a constant applied stress, there was a critical size at which the nucleation of partial dislocations was more probable; when compared to that of perfect dislocations.

On the Nucleation of Partial Dislocations in Nanoparticles. C.E.Carlton, L.Rabenberg, P.J.Ferreira: Philosophical Magazine Letters, 2008, 88[9-10], 715-24