Berlin 2005 – wissenschaftliches Programm

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M: Metallphysik

M 40: Diffusion I

M 40.3: Vortrag

Dienstag, 8. März 2005, 11:00–11:15, TU H2038

Grain Boundary Radiotracer Diffusion and Segregation of Fe and Ni in Polycrystalline Cu — •Jens Ribbe, Sergiy Divinski, Guido Schmitz, and Christian Herzig — Institut für Materialphysik, Universität Münster,Wilhelm-Klemm-Str. 10, 48149 Münster, Germany

⁵⁹Fe and ⁶³Ni grain boundary (GB) diffusion in high-purity Cu was measured by the radiotracer method combined with mechanical sectioning technique in an extended temperature interval. At higher temperatures the conditions of Harrison’s B kinetics were satisfied and the triple product P=s·δ· D_gb of the segregation factor s, GB width δ, and the GB diffusivity D_gb was determined at selected temperatures. Performing GB diffusion measurements at lower temperatures under the C regime conditions, the GB diffusion coefficient D_gb was directly measured. Using the estimate of the GB width deduced from GB self-diffusion measurements on FCC metals, δ≈5·10⁻¹⁰ m, the segregation factor s of Fe was determined as s=P/δ D_gb. Fe reveals high segregation and very slow diffusivity D_gb in Cu high-angle GBs. However, the measured triple product P^Fe for Fe GB diffusion is by orders of magnitude larger than the GB diffusivity P^Ni of Ni. The main reason is the strong GB segregation of Fe in Cu.