EXAFS studies on Al-Cu alloys

Abstract EXAFS spectra of three forms of Al-Cu alloys, namely solid solutions, dispersed G.P. zones and the θ' phase, have been obtained using synchrotron radiation. The well-known structure of the θ' phase has been used to check the validity of the theoretical parameters which enter into the analysis. These experiments lead to an understanding of the core effect around the copper atom in solid solution, the chemical composition of the G.P. zone and the correlated local deformation of the surrounding matrix. In the solid solution the average distance between Cu and its Al nearest neighbours is 2.725 ± 0.02 A, compared to 2.86 A for the Al-Al distance in the matrix. G.P. zones are shown to be monolayers with an average 50-50 composition and the spacing between the two (200) planes is measured to be 1.68 A, compared to 2.0225 A for the d200 in the matrix.