Investigation of the composition and structure of GP zones in - Ag by means of positron annihilation

Positron annihilation spectroscopy is used to obtain information about structures and concentrations of - and -GP zones in - Ag alloys. Measurements of positron lifetimes and Doppler broadening are reported. For the interpretation we present a method to estimate numerically the lifetimes of positrons trapped in spherical precipitates and give results for a series of possible concentrations and internal structures of the precipitated particles. From a comparison with the experimental data we conclude that the silver atoms are distributed homogeneously inside the -GP zones and that the silver concentration of both types of zone is .