Self-diffusion along screw and edge dislocations in Al was studied by molecular dynamics simulations (table 9). Three types of simulations were performed: with pre-existing vacancies in the dislocation core, with pre-existing interstitials, and without any pre-existing defects (intrinsic diffusion). It was found that diffusion along the screw dislocation was dominated by the intrinsic mechanism, whereas diffusion along the edge dislocation was dominated by the vacancy mechanism. Diffusion along the screw dislocation was found to be significantly faster than diffusion along the edge dislocation, and both diffusivities were in reasonable agreement with experimental data. The intrinsic diffusion mechanism could be associated with the formation of dynamic Frenkel pairs, possibly activated by thermal jogs and/or kinks. The simulations showed that at high temperatures the dislocation core became an effective source/sink of point defects and the effect of pre-existing defects on the core diffusivity diminishes.

A Molecular Dynamics Study of Self-Diffusion in the Cores of Screw and Edge Dislocations in Aluminum. Pun, G.P.P., Mishin, Y.: Acta Materialia, 2009, 57[18], 5531-42

Table 9

Arrhenius parameters for diffusion along

screw and edge dislocations in Al