Direct determination of grain-boundary and dislocation self-diffusion coefficients in silver from experiments in type-C kinetics

Abstract

The use of an implanted, mass-separated carrier-free 105Ag radiotracer improves the sensitivity for measuring grain-boundary (GB) penetration profiles. In this way the GB self-diffusion coefficient DGB in silver was directly determined from experiments in type-C kinetics conditions. When multiplying the DGB values with a GB width δ=0.5 nm the results are in agreement with GB diffusivities P=δDGB measured in the same Ag material in the usual type-B kinetics experiments which were performed between 911 and 540 K and extrapolated to the low-temperature regime of type-C kinetics experiments (455–353 K). From the near-surface part of the type-C diffusion profiles the dislocation diffusion coefficient Dd was directly determined. These Dd values are compared with experiments of Turnbull and Hoffman [Acta Metall. 2, 419 (1954)] who applied the dislocation pipe model for a low-angle-tilt GB in silver. The good agreement confirms a dislocation core diameter of about 0.5 nm.