Berlin 2008 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 6: Diffusion I

MM 6.5: Vortrag

Montag, 25. Februar 2008, 11:15–11:30, H 0111

Early stages of precipitation in AlMgSi alloys: an investigation by positron annihilation — •Benedikt Klobes, Torsten E. M. Staab, Matz Haaks, and Karl Maier — Helmholtz-Institut für Strahlen- und Kernphysik, Nußallee 14-16, D-53115 Bonn

Aluminium alloys on the basis of AlMgSi, the so-called 6000 series, are commonly used in a wide range of industrial applications due to their good mechanical properties as well as their weldability. These properties are induced by the precipitation of nanoscaled agglomerates of Mg and Si atoms which are formed during specific heat treatments. Although these alloys have been the object of intense investigations, it has been impossible to reveal the atomic structures of these precipitates up to now. Thus, the understanding of the precipitation sequence remains incomplete. Measuring the positron lifetime and the Doppler broadening of the annihilation radiation directly after solution heat treatment and quenching we recently observed a significant change of the mean positron lifetime as well as the momentum distribution during subsequent storage at room temperature. The first stages of precipitation could be investigated in both high purity alloys and a commercial alloy AA6013 this way. With these results we hope to throw a little light on the controversially discussed precipitation sequence of AlMgSi alloys.