| Zusammenfassung: |
We propose X-ray absorption (XAS) measurements as a novel approach to determine the atomic structure of pre-Guinier-Preston zones. These nano-clusters are formed during very early stages of aging AlCu alloys, immediately after solution heat treatment and quenching. X-ray absorption near-edge structure (XANES) spectra were taken from technical aluminum alloys at the copper K edge, revealing the local atomic environment of copper. The spectra of - after solution heat treatment - freshly quenched and of artificially aged alloys differ significantly from each other. We compare the measured XANES spectra with those calculated by the FEFF-8 code. We show the importance of employing realistic, i.e. relaxed, atomic coordinates around the scattering atom type from ab-initio calculations with SIESTA. Atomic structure of a pre-GPZ from SIESTA: a small disk of five Cu atoms (red) on a 100 plane in fcc Al (blue). Note that Al atoms in direct neighborhood of copper relax towards the small Cu disk. (online colour at: www.pss-rapid.com) (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
, M. Haaks