Effect of pre-deformation on microstructure and mechanical properties of a fine-grained 2A97 alloy

This study investigates the effect of pre-deformation by cold rolling after solution annealing on the microstructure and properties of the fine-grained Al-Li alloy 2A97. Electron backscatter diffraction (EBSD), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize grain boundaries, dislocations, precipitates and calculate their contribution to strength. It is found that the changes in precipitation behavior predominantly account for the enhanced tensile properties observed in the deformed alloys, where yield and tensile strengths are increased by 85 MPa and 63 MPa, respectively. The peak-aged samples without pre-deformation are mainly strengthened by the T₁ phase, δ'/θ'/δ' composite and σ phase. In contrast, deformation of 10 % prior to aging facilitates the precipitation of the T₁ and lath-like S phases while concurrently inhibiting the precipitation of the σ phase and δ'/θ'/δ' composite phases. In addition, for fine-grained alloys, low-angle grain boundaries induce the precipitation of the finer T₁ phase compared to the T₁ phase located inside the grain, which contributes to the good performance of 2A97 alloy.