Effect of cold rolling on nucleation, growth and coarsening of S-phase precipitates in Al- Cu- Mg alloy (AA2024): From heterogeneous nucleation to homogeneous spatial distribution

Abstract

The effect of cold rolling on the precipitation kinetics of the hardening phase has been studied in industrial AA2024. Due to the relatively simple precipitation sequence and the use of the alloy in naturally aged (T3) and peak-aged (T8) states, it was possible to unambiguously analyse the effect of pre-deformation on the nucleation/growth and coarsening of the S-phase. Faster coarsening kinetics due to dislocations induced by cold rolling were observed before the recovery had been completed, leading to lower hardness of pre-deformed AA2024-T8 compared to that without pre-deformation for the same ageing conditions. The nucleation and growth of S-phase were also faster after cold rolling. Moreover, the heterogeneous nucleation resulting from pre-deformation finally led to a fine and homogeneous spatial distribution of hardening precipitates and thus to higher hardness values. Furthermore, cold rolling resulted in a different aspect ratio of S-phase precipitates during both growth and coarsening. The current study was conducted on AA2024, one of the most studied Al-Cu-Mg alloys, where only one equilibrium phase, the S-phase, precipitates, but the findings may be applicable for other precipitation-hardened alloys as well.