Abstract:The evolution of the S'''' precipitate in Al-Cu-Mg alloy was investigated using transmission electron microscopy (TEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), molecular dynamics (MD) simulations, and other analytical techniques. The precipitation behavior during different aging stages of the supersaturated solid solution formed after rapid cold punching was focused, which induces rapid dissolution of precipitates. The findings reveal that the precipitation sequence is significantly influenced by aging temperature. At higher aging temperatures, which mitigate lattice distortion in the matrix, the precipitation sequence follows the conventional path. Conversely, at lower aging temperatures, where lattice distortion persists, the sequence deviates, suppressing the formation of Guinier-Preston-Bagaryatsky (GPB) zones. MD simulations confirm that the variations in solute atom diffusion rates at different aging temperatures lead to the differences in the S'''' phase precipitation sequence.

Key words: Al-Cu-Mg alloy; aging treatment; S'' phase evolution; rapid cold punching; molecular dynamics simulations