A detailed study of the precipitation of the γ(Ag2Al) phase in undeformed aluminium-silver alloys was conducted. Several previously unreported features were observed, including the formation of discrete three-dimensional assemblies composed of five-seven precipitates on faulted dislocation loops. The precipitate assemblies adopted a morphology approximating a tetrahedral bipyramid. The bounding defect of the stacking fault was found to control both the nucleation of additional precipitates, which was responsible for the formation of the assembly structure, and also the growth characteristics of individual precipitates with these assemblies.

Precipitate Assemblies Formed on Dislocation Loops in Aluminium-Silver Alloys. J.M.Rosalie, L.Bourgeois, B.C.Muddle: Philosophical Magazine, 2009, 89[15], 1267-78