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M: Metallphysik

M 27: Nanoskalige Materialien I

M 27.3: Fachvortrag

Donnerstag, 29. März 2001, 10:45–11:00, S5.3

Fe-Diffusion in grain-boundaries of nanocrystalline Fe₁₄Nd₂B — •F. Ye¹, M. Eggersmann¹, O. Gutfleisch², S. Herth¹, and R. Würschum^1,3 — ¹Institut für Nanotechnologie, Forschungszentrum Karlsruhe, Postfach 3640, 76021 Karlsruhe — ²Institut für Festkörper- und Werkstofforschung Dresden, Postfach 270016, 01171 Dresden — ³Institut für Technische Physik, TU Graz, Petersgasse 16, A-8010 Graz

Despite the great technical relevance of Fe₁₄Nd₂B as high energy density permanent magnet, no data on the self-diffusion in this system are available. This is remarkable in view of the fact that diffusion, in particular, in the intergranular liquid films formed in Nd-rich alloys at high temperatures, is of great importance for the metallurgical processing of these materials. The present work aims at grain-boundary (GB) diffusion studies in Fe₁₄Nd₂B below and above the intergranular melting transition using the radiotracer technique with the isotope ⁵⁹Fe. A preliminar evaluation of the diffusion profiles on the basis of grain-boundary diffusion kinetics of type B yields the product D_GB δ = 2.7 · 10⁻¹¹  exp (1.8 eV/kT) m³s⁻¹ of the grain boundary diffusivity D_GB and thickness δ in the solid phase assuming a volume self-diffusivity as in α-Fe. First results obtained for the liquid grain-boundary regime are presented.