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Title: Atomic structure of pre-Guinier-Preston and Guinier-Preston-Bagaryatsky zones in Al-alloys
Author(s): T. E. M. Staab Person, B. Klobes Person, I. Kohlbach Person, B. Korff Person, M. Haaks Person, E. Dudzik and K. Maier Person
Journal: J. Phys.: Conf. Ser.
Year: 2011
Volume: 265
Issue: 1
Pages: 012018
DOI: 10.1088/1742-6596/265/1/012018
File URL: http://stacks.iop.org/1742-6596/265/i=1/a=012018
Abstract: We present results on the structure of nano-sized particles (Guinier-Preston (GP) and Guinier-Preston-Bagaryatsky (GPB) zones) in Aluminum alloys. Precipitates of alloying elements like Cu, Mg, or Si hinder the motion of dislocations and, thus, are responsible for the strength of AlCuMg- and AlMgSi-alloys - used e.g. as AA2024 (old aircrafts) and AA6013 for the fuselage of the new Airbus A380, respectively. We will discuss the role of quenched-in vacancies for diffusive motion at room temperature (RT) enabling the growth of the precipitates. Using positron annihilation spectroscopy (PAS) – both lifetime and Doppler broadening – gives information on the local atomic environment in the vicinity of vacancies. On the other hand X-ray absorption fine structure (XAFS) spectroscopy is capable of characterizing the local atomic environment around selected elements (Cu, Mg). We will interpret the measured data by comparing them to numerical calculations of PAS and XAFS spectra. However, reliable numerical calculations of spectroscopic quantities are only possible provided that relaxed atomic positions are used as an input. We calculate those employing the ab-initio code SIESTA. Thus, considering decomposition of Al-alloys, we obtain extremely valuable information on the earliest stages, forming immediately after solution heat treatment and quenching, i.e. during the first few minutes of storage at RT.

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