Dresden 2009 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 29: Diffusion and Point Defects II
MM 29.2: Vortrag
Mittwoch, 25. März 2009, 12:15–12:30, IFW D
Calculations of positron annihilation properties for sub-nano precipitates in Al-Mg-Cu alloys — •Björn Korff1, Iris Kohlbach1, Benedikt Klobes1, Torsten Staab2, Matz Haaks1, and Karl Maier1 — 1Helmholtz-Institut für Strahlen- und Kernphysik Universität Bonn — 2Fraunhofer Institut für Silicatforschung Würzburg
Early stages of precipitation in age-hardenable aluminum alloys affect the final strength of the alloys by the formation of certain kinds of nuclei. Even though consisting of just a few atoms, these nuclei determine the further growth of precipitates responsible for hardening the alloy.
For their structural analysis we use positron annihilation spectroscopy. In this way we obtain information about the local atomic structure inside precipitates, but especially around vacancies. The interpretation of measurements is assisted by calculations simulating measurable positron annihilation parameters for different possible atomic configurations.
Positron measurements of alloys with aging times from a few minutes to eight hours are compared with calculations for several structures representing candidates for first nuclei of precipitation. This way we learn about the agglomeration of Mg and Cu mediated by the diffusion of quenched-in vacancies and about their arrangement prior to the formation of larger stable structures.