Dresden 2006 – wissenschaftliches Programm
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MM: Metall- und Materialphysik
MM 5: Phase transitions II
MM 5.6: Vortrag
Montag, 27. März 2006, 13:00–13:15, IFW D
Primary crystallization of the hypoeutectic Ni-17at.% P alloy by ASAXS — •Rainer Kranold1, Dragomir Tatchev2, Günter Goerigk3, and Stephan A. Armyanov2 — 1Institut für Physik, Universität Rostock, D-18051 Rostock, Germany — 2Institute of Physical Chemistry, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria — 3Institut für Festkörperforschung, Forschungszentrum Jülich, PF 1913, D-52425 Jülich, Germany
During the primary crystallization of a hypoeutectic Ni-P alloy, according to the equilibrium phase diagram, crystallites of pure Ni should be precipitated until the matrix reaches the eutectic composition with 19 at.% P. However, several authors assume that the precipitating Ni particles contain a certain P amount. We investigated with anomalous small-angle X-ray scattering (ASAXS) the primary crystallization of Ni(P) particles in the amorphous hypoeutectic Ni-17 at.% P alloy. Using the maximum entropy method, the particle size distribution, the size dependence of the particle composition and the amorphous matrix composition could be found simultaneously. The size distribution consists of a peak at particle radius of 1 nm and a tail spanning from 2 to 15 nm. The composition of the particles of the peak changes from 14 to 2 at.% P as their radius grows from 0.7 to about 3 nm. The particles in the tail of the size distribution (2-15 nm) have nearly constant P content in the range of 0-2 at.%. The matrix composition tends to the eutectic one at the end of the primary crystallization process. Our experimental results comply the predictions of a new nucleation theory developed recently [1]. [1] D. Tatchev et al., J. Appl. Cryst. 38 (2005) 787