Investigation of in-plane anisotropy in tensile properties and creep aging behavior of largely pre-deformed Al–Cu–Li alloy

Largely pre-deformed Al–Cu–Li alloy sheets exhibit enhanced creep formability and strength but introduce substantial in-plane anisotropy. This study systematically investigates the effects of pre-deformation (75 % vs. 5 % reduction) on creep aging behavior and tensile properties at orientations of 0°, 45° and 90° relative to the rolling direction. Results reveal that 75 % pre-deformation leads to a fibrous microstructure and increased dislocation density, particularly at 0°, resulting in the highest creep strain (0.244 %) and tensile strength (592 MPa). However, this orientation also exhibits the largest in-plane anisotropy, with in-plane anisotropy index of 46.9 % for creep strain and 5.6 % for tensile strength. Digital image correlation demonstrates that strain localization and crack propagation align with elongated grains, while transmission electron microscopy confirms slender dislocation walls at 0° and thick walls at 90°, which reveals that anisotropic dislocation structures and grain morphology synergistically govern the mechanical anisotropy. These results emphasize that while large pre-deformation improves creep and strength at 0°, it intensifies anisotropy, necessitating careful design considerations for aerospace applications.