Aging behavior of an Al–Cu–Mg alloy

Highlights: • Natural aging of an AA2519 alloy leads to precipitations of GP and GPB zones. • Artificial aging produces θ″/θ′- and Ω-phase plates. • 0.7 and 3.3 wt%Cu are consumed for the formation of θ″ and θ′-phases. • Natural aging provides the best combination of strength and ductility. Effect of aging temperature on precipitation behavior and mechanical properties of an AA2519 alloy was examined. Long-term natural aging provides the best combination of strength and ductility by the precipitation of dense Guinier–Preston and Guinier–Preston–Bagaryatsky zones. This phenomenon, called "delayed hardening", has the same origin as the "rapid hardening" in AA2X24 alloys subjected to artificial aging. At 190 °C, high density of θ″-phase provides high strength. Peak aging is characterized by insignificant increase in strength associated with additional precipitation of θ′-phase. The overaging leads to the formation of precipitate structure dominated by θ′-phase. The formation of θ″- and θ′-phases can consume ∼0.7 and ∼3.3%Cu, respectively. Despite this, the number density of θ″-phase precipitates is higher than that of θ′-phase ones by a factor of ∼40. The θ″-phase is effective strengthening agent in the AA2519 alloy. The Ω-phase plates with a very high aspect ratio (AR) > 100 precipitate during artificial aging.