Investigation of the crystallography and morphology of the S′ precipitate in an Al(CuMg) alloy by HREM

Abstract
The crystal lattice of the S′ phase in a 2024 aluminium alloy with 4·43 wt% Cu and 2·00 wt% Mg, and the precipitate–matrix orientation relationship are directly illustrated by the [100] lattice image of both the S′ and matrix phases. Two types of the precipitation morphology of the S′ phase, which correspond to homogeneous and preferential nucleation respectively, are also shown.