Accelerated age hardening by plastic deformation in Al–Cu with minor additions of Si and Ge

An extremely fast hardening response with no reduction in peak hardness was obtained in Al–Cu with minor additions of Si and Ge by 8% plastic deformation before artificial aging. The mechanism for the accelerated hardening was determined by detailed characterization with transmission electron microscopy. Plastic deformation was found to enhance the nucleation rate of Si–Ge precipitates, resulting in a higher volume density. Such precipitates catalyzed the formation of θ′ precipitates that are responsible for hardening.