Temperature dependence and anisotropy of grain boundary self-diffusion along Σ = 5 〈001〉 tilt boundaries in Ag

Abstract

Using the radiotracer 110mAg, grain boundary (GB) self-diffusion in naturally grown, symmetrical Σ = 5〈001〉 tilt boundaries has been studied in detail resulting in the first extended set of self-diffusion data for oriented high-angle GBs. A technique based on the Bridgman method has been developed which allows production of GBs with large area (∼8 × 60mm). This allows the measurement of the diffusion behaviour parallel and perpendicular to the tilt axis in specimens cut from the same bicrystal. The GB diffusivity was measured for diffusion parallel and perpendicular to the tilt axis in the temperature range 593–876 K. The Arrhenius parameters determined for the θ = 53.1° 012 GB were found to be drastically lower (1.23 × 10 −17 m 3s −1; 37.4 kJ/mol) than for the θ = 36.9° 013 GB (6.44 × 10 −13 m 3s −1; 109.1 kJ/mol). Furthermore, a slight anisotropy was found for θ = 36.9°, but no anisotropy was observed for θ = 53.1°. This behaviour is rationalized using a three-dimensional model of the atomic structure in the GB core region.