Study on the Synergistic Effects of Pre-Deformation and Post-Aging Treatments on the Mechanical and Corrosion Properties of a 2A97 Al-Cu-Li Alloy

This work systematically investigates the effects of pre-deformation, post-aging temperature, and aging time on the mechanical properties, corrosion behavior, and microstructure of a 2A97 Al-Cu-Li alloy. Microstructural characterization indicates that the main precipitates are T1 (Al2CuLi), δ′ (Al3Li), θ′ (Al2Cu), and S′ (Al2CuMg). At 160 °C with 0% pre-deformation strain, increasing aging time increases the size and number density of T1, changing the size and number density of δ′ and θ′ accordingly, whereas raising the aging temperature to 180 °C mainly coarsens precipitates. Increasing pre-deformation from 0% to 12% increases T1 number density and refines its size. Significantly, after aging at 180 °C, θ′ is absent in the 8% and 12% pre-deformed alloys, and T1 re-dissolves in the over-aged 12% alloy. Grain-boundary (GB) phases evolve from fine/discontinuous (under-aged) to fine/continuous (peak-aged) to coarse/discontinuous (over-aged). At the same time, higher pre-strain reduces their size, and higher aging temperature promotes coarsening. Higher aging temperature and pre-deformation accelerate age hardening and shorten the peak-aging time. In the peak-aged state, strength increases but elongation decreases with increasing pre-deformation or aging temperature. Among all, the 4% pre-deformed alloy aged at 160 °C for 30 h shows optimal room-temperature properties, i.e., ultimate tensile strength ~613 MPa, yield strength ~564 MPa, and total elongation ~6.91%. Corrosion resistance was closely related to microstructural evolution during aging, and both prolonged aging and increased pre-deformation decreased the susceptibility to intergranular corrosion. The results provide a basis for optimizing the thermomechanical processing of 2A97 Al-Cu-Li alloys.