Microstructural evolution and mechanical response of AA2099 Al–Li alloy regulated via thermal rolling pre-aging process

The AA2099 Al–Li alloy is widely used in aerospace structures owing to its high specific strength and low density. However, achieving an optimal balance between strength and ductility remains challenging under conventional heat treatment processes. In this study, a thermomechanical processing route comprising solution treatment, hot-rolling pre-deformation, and artificial aging was employed to enhance the mechanical properties of AA2099 while maintaining good ductility. At 10 % hot-rolling pre-deformation, the alloy exhibited a tensile strength of 605 ± 10.4 MPa and an elongation to fracture of 6.7 % ± 0.4. The strength increase was attributed to the optimized hot-rolling pre-deformation, which not only increased the contribution of dislocation strengthening but also raised the volume fraction of the T 1 (Al 2 CuLi) precipitates, thereby enhancing the precipitation-strengthening effect. Under low pre-deformation, the formed dislocation structures allowed the material to retain the capacity for further dislocation accumulation during tensile loading, thus preserving ductility. With increasing pre-deformation, the diameter of the T 1 precipitates gradually decreased, which, although beneficial for improving ductility, correspondingly reduced the contribution of precipitation strengthening. These findings deepen understanding of how deformation influences aging behavior and provide practical strategies for process optimization to achieve a desirable strength-ductility balance in Al–Li alloys.