Dresden 2006 – scientific programme

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MM: Metall- und Materialphysik

MM 8: Symposium Modern Metallic Materials Design II

MM 8.6: Talk

Monday, March 27, 2006, 16:00–16:15, IFW B

Are Guinier-Preston Zones in Al-Alloys stabilized by Grown-inStructural Vacancies — •Torsten E.M. Staab, Michael Roebel, and Karl Maier — Helmholtz Institut für Strahlen- und Kernphysik,Rheinische Friedrich-Wilhelms-Universität Bonn, Nußallee 14-16,D-53115 Bonn, Germany

Aluminum alloys obtain their strength by nanometer-sized precipitations of their alloying elements, which are effectively hindering the dislocation motion. The morphology of precipitations varies from spherical via ellipsoidal to plate- or needle-like structures. Recent ab-initio calculations on a plane of 14 Cu atoms – not containing any vacancies – in aluminum showed that this structures are unstable [1]. However, structural vacancies may be found in precipitations as-grown after solution heat treatment, quenching to water, and subsequent ageing. By the SIESTA ab-initio code we calculate the formation energies for vacancies in aluminum and their binding energy to substitutional atoms of the alloying elements for Al-Ag, Al-Cu and Al-MgSi. Additionally, we determine the formation and binding energies for vacancies inside the precipitations in these materials, since important classes of technical alloys used in outer shell plates of airplanes are based on AlCu or AlMgSi. The results of the ab-initio calculations will be compared to positron annihilation experiments on AA2024 and AA6013 alloys.

[1] M. Röbel, Dissertation University Bonn, 2005