Influence of temperature and strain rate on the competition between dynamic precipitation and dynamic dissolution in an aged 7xxx Aluminum alloy

Warm forming of high strength Aluminum alloys is a promising process for avoiding the low formability intrinsic to these precipitation-strengthened materials. However, during a process combining temperature and strain, precipitates undergo complex a dynamic evolution due to the plastic strain, which is not quantitatively understood in terms of influence of initial temper, strain, strain rate and temperature. Deformation can both induce precipitate dissolution due to shearing or accelerate the precipitation kinetics by producing excess vacancies. In this work, Small Angle X-ray Scattering in situ tensile tests have been performed on aged Al-Zn-Mg-Cu samples over a wide parameter space to understand the influence of deformation on precipitation. A competition between dynamic dissolution and dynamic precipitation has been highlighted, which depends on the temperature and the strain rate. Dynamic dissolution mainly depends on strain. Conversely, dynamic precipitation is a diffusive process, and therefore depends on the deformation temperature and the deformation duration. This competition has been confirmed by selected atom probe tomography observations. Dynamic precipitation in Al-Zn-Mg-Cu T6-aged alloy In-situ SAXS during tensile test enables determining the evolution of precipitate size distribution Competition between dynamic dissolution and dynamic precipitation depends on T, ε ˙