Radiotracer investigation of silver grain boundary diffusion and segregation in copper bicrystals at low temperatures: the direct determination of grain boundary diffusion coefficients

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The project is focused on the experimental investigation of grain boundary diffusion of Ag in Cu bicrystals. Precisely characterized near Σ5 bicrystals will be investigated. We have recently improved the sensitivity and precision of the radiotracer measurements so that, for the first time, grain boundary diffusion in a bicrystal will be determined at such low temperatures that the so-called C-type kinetic conditions will be satisfied. These measurements will provide directly the values of the solute grain boundary diffusion coefficients, Dgb, which were never measured so far in bicrystals. At higher temperatures the measurements will be performed in the so-called B-type kinetics, which yield the triple product values, , P = s • δ • Dgb, where s is the segregation factor and ± the grain boundary width. The combination the low- and high-temperature measurements performed both along and perpendicular to the tilt axis of the oriented bicrystal is the key of the project and the product s • δ and its probable anisotropy will be determined for the first time. Considerable improvement of the current understanding of grain boundary diffusion and segregation phenomena is expected from this in its completeness so far unique investigation.