Deformation can enhance the precipitation kinetics from an aluminium alloy supersaturated solid solution. Particularly, when deformation is applied at the ageing temperature, both nucleation rate and growth rate of the precipitates can be strongly influenced. At ambient or moderate warm forming temperature this phenomenon has been attributed to deformation-enhanced vacancy concentration, which can be increased by orders of magnitude above the thermal vacancy concentration. The enhanced vacancy concentration directly increases the diffusivity of substitutional species, and can also influence the clustering processes that result in nucleation.

Previous studies suggest the nature of the dynamic precipitation is strongly related to the deformation temperature and strain rate. A classical model for the excess vacancies effect developed by Militzer et al. predicts that both strain dependent/strain rate independent and strain rate dependent/strain independent regimes are possible in aluminium alloys depending on conditions. To quantify this, experiments are required over a range of strain rates and temperatures. Previous studies have focused on low strain rates (<10^-3 s^-1), but to investigate conditions closer to those encountered in commercial warm forming, higher strain rate studies were performed.

In the present study, the dynamic precipitation in commercial AA7075 was studied during deformation in tension using a dilatometer across a range of deformation temperatures (120℃, 150℃ and 180℃) and at two strain rates faster than previously investigated (10^-1 and 1 s^-1). The precipitates in the final microstructure were characterized with the help of the synchrotron small-angle X-ray scattering and transmission electron microscopy. The temperature and strain rate dependence of the precipitate evolution kinetics under these conditions has been assessed and compared with results from previous work and predictions of the Militzer et al. excess vacancy model.