Atomic mechanisms of precipitate plate growth in the AlAg system—I. Conventional transmission electron microscopy

Abstract

The detailed interfacial structure of γ′ precipitates in an Al-15 wt%Ag alloy has been studied by conventional transmission electron microscopy. Contrast analyses indicate that there is a strong tendency for single 1 6 〈112〉 Shockley partial dislocations on the precipitate faces to interact, forming multiple-unit ledges which display the contrast behavior of 1 2 〈110〉 dislocations. In addition, both the edges of these precipitates and ledges on the edges are comprised of the same partial dislocations stacked vertically or slightly behind one another. All three variants of Shockley partials have been observed on the same {111} faces of precipitates, and all interfaces of the precipitates display a strong preference for 〈110〉 configurations. The similarities between growth of ledges on the broad faces and the edges of precipitates by a kink mechanism are described and explained.