Early stages of decomposition in Al alloys investigated by X‐ray absorption

We demonstrate the sensitivity of X‐ray absorption fine‐structure (XAFS) measurements to the earliest stages of decomposition in Al alloys, i.e. just a few minutes after quenching. XAFS is one of the few applicable experimental approaches to this regime. Three different AlCu(Mg) samples were investigated by XAFS at the Cu K edge. Significant changes of the XAFS can be detected in the course of the decomposition in these alloys during the first 15 minutes. Actually, these changes correspond to relaxations of the nearest neighbours towards the absorbing Cu atoms. The Fourier transformation of the XAFS spectra thus leads to a pseudo radial distribution function which reflects this relaxation. In addition, XAFS measurements of the S‐phase of AlCuMg are used to decide in favour of the Perlitz and Westgren model for the S‐phase. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)