Reinforcement Mechanism of Initial Stress on Artificial Aging of 2198 Al–Cu–Li Alloy Sheet

This study investigates the effects of applied stress during artificial aging on the 2198 Al–Cu–Li alloy. The results demonstrate that after artificial aging at 145 °C, the 2198 Al–Cu–Li alloy primarily features densely distributed δ′ phases with larger diameters as the main strengthening phase. The application of initial stress during aging at 145 °C induces δ′ phase dissolution, resulting in a 54.8% reduction in δ′ phase density, accompanied by a 4.8% decrease in yield strength. At an artificial aging temperature of 165 °C, a small quantity of T ₁ phases begins to precipitate in the matrix, accompanied by δ′ phase dissolution, leading to simultaneous reductions of 13.9% in yield strength. When 200 MPa initial stress is applied to artificial aging at 165 °C, the number of δ′ phases further decreases with a noticeable reduction in diameter, while a substantial amount of T ₁ phases precipitates with increased thickness, reduced diameter, and uniform distribution. The yield strength of this state is 60.8% higher than that of AA‐165. The influence of stress on the artificial aging treatment of 2198 Al–Cu–Li alloy thin plates mainly lies in accelerating the dissolution of δ′ phase and promoting the precipitation of T ₁ phase.