THE STRUCTURE OF GP ZONES IN AN AL-CU-ZN ALLOY

An Al-1.46 at.% Cu-2.20 at.% Zn crystal was quenched and aged at 353 K for 24 h. Anomalous dispersion was used to separate the effects of Cu and Zn in the diffuse scattering by measuring the diffuse scattering in absolute units at two different energies for each respective absorption edge. The scattering contrast between these two conditions near each edge was analyzed to get the short range order parameters for Al-Cu and Al-Zn pairs. Via computer simulation with these parameters the Cu was found to lie in small {100} plates and the Zn in short <110> strings that probably lie on planes adjacent to the Cu plates.