A critical evaluation of x-ray small angle scattering parameters by transmission electron microscopy: GP zones in Al alloys

Abstract

The relation of x-ray small angle scattering parameters to transmission electron microscopy results for spherical GP zones is investigated. The Guinier radius is found experimentally to equal (R ⁷/R ⁵)^½ and the Porod radius to equal R ³/R ². This result had been theoretically predicted by Baur and Gerold (1964). It was further found that a log normal distribution closely fits the experimental data. The use of this distribution allowed the size distribution curve of spherical GP zones to be constructed from the x-ray parameters and a knowledge of the metastable miscibility gap. This result is used to follow the evolution of size distribution in both Al-Ag and Al-Zn alloys. The application of this approach to nucleation and growth as well as redistribution processes is discussed.