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

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, 0') in creep-aged Al-Cu-Li alloy was directly attributed to the loading directions. The number density of T-1-phase in the creep-aged single crystal loaded close to < 001 >(infinity) direction is highest, and that of T-1-phase is the lowest when the loading direction is < 111 >(infinity). Moreover, the oriented-precipitation of T-1-phase was found in the creep-aged sample loaded close to < 111 >(infinity) direction, while that of theta' -phase was observed in the creep-aged sample loaded close to < 011 >(infinity) 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 >(infinity) for the Al-Cu-Li alloy to obtain better mechanical property. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

This study investigates the precipitation behavior of an Al-Cu-Li single crystal during creep aging under different loading orientations using high angle annular dark field-scanning transmission electron microscope (HAADF-STEM) observation. The results show that the number density of T1-phase precipitates in the creep-aged alloy is directly affected by the loading directions, with the highest density observed when the loading direction is <001>(infinity) and the lowest density when it is <111>(infinity). In addition, oriented precipitation of T1-phase is found in the sample loaded close to <111>(infinity) direction, whereas theta'-phase is observed in the sample loaded close to <011>(infinity) direction. The hardness evolution of the creep-aged samples aligns with the precipitation behavior. This work proposes a novel method to regulate the precipitation behavior of the creep-aged Al-Cu-Li alloy by controlling the loading direction, with <001>(infinity) being the ideal loading direction for better mechanical properties.