Relationship between precipitation behavior and loading orientations of the creep-aged Al–Cu–Li single crystal

Abstract

In present work, typical loading orientations were applied on an Al–Cu–Li single crystal during creep aging, and the relationship between precipitation behavior and loading orientations of the creep-aged Al–Cu–Li single crystal was studied by high angle annular dark field - scanning transmission electron microscope (HAADF-STEM) observation along multiple zone axes. The results show that the precipitation behavior of the precipitates (i.e., T1, θ′) in creep-aged Al–Cu–Li alloy was directly attributed to the loading directions. The number density of T1-phase in the creep-aged single crystal loaded close to <001>α direction is highest, and that of T1-phase is the lowest when the loading direction is < 111>α. Moreover, the oriented-precipitation of T1-phase was found in the creep-aged sample loaded close to <111>α direction, while that of θ′-phase was observed in the creep-aged sample loaded close to <011>α direction. The hardness evolution of the creep-aged samples along different loading orientations is also in agreement with the corresponding precipitation behavior. The present work proposes a novel method to regulate the precipitation behavior of the creep-aged Al–Cu–Li alloy by controlling the loading direction, and the ideal loading direction is < 001>α for the Al–Cu–Li alloy to obtain better mechanical property.