Dresden 2006 – wissenschaftliches Programm

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MM: Metall- und Materialphysik

MM 42: Diffusion II

MM 42.2: Vortrag

Freitag, 31. März 2006, 11:15–11:30, IFW B

Towards the influence of bulk solubility on grain boundary segregation: a case study of Fe and Ni diffusion in Cu — •Jens Ribbe, Sergiy Divinski, Guido Schmitz, and Christian Herzig — Institut für Materialphysik, Universität Münster

⁵⁹Fe and ⁶³Ni grain boundary (GB) diffusion in high-purity Cu was measured by the radiotracer method combined with mechanical sectioning 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 C regime condition, 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 and Ni was determined as s = P/ δ D_gb. Fe reveals strong segregation and very slow diffusivity D_gb in Cu high-angle GBs. The measured triple product P^Fe for Fe GB diffusion is by orders of magnitude larger than the GB diffusivity P^Ni of Ni and many other elements. Small bulk solubility and strong segregation resulted in unusual penetration profiles of GB diffusion of Fe in the B kinetics. The nature of this phenomenon is discussed.