Dynamic precipitation kinetics in an Al-Cu alloy

Precipitation hardening alloys are increasingly used for vehicle lightweighting. A critical property for these applications, formability, is poor in these high strength alloys, which has led to the development of warm forming processes. In these conditions, dynamic interactions exist between plastic deformation and precipitation, which are not yet fully understood. This work investigates the precipitation kinetics in an Al-Cu alloy, the AA2219 alloy, comparatively during aging at 200°C without deformation, with a pre-deformation prior to aging and with a warm deformation during aging. The in-situ Small-Angle X-ray scattering measurements demonstrate that the precipitation kinetics is accelerated by plastic deformation, all the more when applied at the aging temperature. Transmission electron microscopy shows that static and dynamic interactions result in qualitatively similar microstructures, showing that the nucleation of precipitates is similar after pre-deformation or during dynamic precipitation. The enhanced kinetics in dynamic conditions is related to the diffusion acceleration caused by the excess vacancies production during plastic deformation.