Self-Diffusion along Edge Dislocations in Nickel

Abstract

We have measured self-diffusion along widely spaced edge dislocations in nickel. A surface-accumulation counting technique was used. The dislocations were arranged to be perpendicular to the surface which was counted and were pure edge in character. The diffusion measurements were carried out in the temperature range of 500 to 600°C where lattice diffusion was not significant. Solutions of the diffusion equation for a variety of boundary conditions are presented. The operative boundary conditions in the present experiment were determined by a tracer-sectioning technique. The diffusivity along the edge dislocations can be described by $D_p^{}{}_{}{}^{\mathrm{edge}}=\left(20\mathrm{} \frac{{\mathrm{cm}}^2}{sec}\right)\left[\exp \right(\frac{-1.6\mathrm{} \mathrm{eV}}{\mathrm{kT}}\left)\right]$ $\frac{D_p^{}{}_{}{}^{\mathrm{edge}}}{D_{\mathrm{bulk}}}=0.55\mathrm{}$. The analysis of the data results in a value for the radius of the high-diffusivity dislocation core of about ${10}^{-7\mathrm{}}$ cm.