Ab initio study of growth mechanism of omega precipitates in Al-Cu-Mg-Ag alloy and similar systems

We investigate nucleation and growth stages of Ω precipitates in Al-Cu-Mg-Ag alloys by using density functional theory calculations. Results show that the Ω-precipitates may initiate from two hexagonal Ag layers embedded inside the planes of the Al matrix with Mg at the center of the hexagons. A ledge structure model constructed from the interfacial atomic structure of the Ω precipitates suggests a mechanism whereby Cu atoms are delivered during ledge migration. The above mechanisms may be extended to similar interfacial structures found in other alloy systems, and can be exploited in designing new nano-precipitates.