Fe-Diffusion in grain-boundaries of nanocrystalline Fe14Nd2B

F. Ye1, M. Eggersmann1, O. Gutfleisch2, S. Herth1 und R. Würschum1,3
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

DGBd = 2.7 · 10-11  exp (1.8 eV/kT) m3s-1 of the grain boundary diffusivity DGB and thickness d in the solid phase assuming a volume self-diffusivity as in a-Fe. First results obtained for the liquid grain-boundary regime are presented.