Influence of the Al₃(Sc,Zr) Dispersoids and the Stretching on the Natural Ageing Behavior of a Binary Al-4 wt%Cu Alloys

Abstract

Aluminum alloys are extensively used in the aerospace industry due to their high specific strength. Combined scandium (Sc) and zirconium (Zr) additions result in the formation of nano-size Al₃(Sc,Zr) dispersoids which considerably increase the mechanical properties of these alloys. Recent research on Al–Cu–Sc–Zr model alloys showed that these dispersoids accelerate the formation kinetics of the copper (Cu) rich precipitates and modify their precipitation sequence. In this work, the effect of Sc and Zr addition and of the stretching on the precipitation during natural ageing of an Al-4 wt%Cu is investigated. Hardness and tensile measurements are used to quantify the hardening kinetics from precipitate formation during natural ageing. Transmission electron microscopy and differential scanning calorimetry are used to characterize the formed precipitates. Although the work hardening experienced during the stretching was significantly higher in the Al–Cu–Sc–Zr alloy, the strength increment during natural ageing was higher in the binary Al–Cu alloy. The presence of Sc and Zr inhibits the formation of GP zones that can explain the lack of mechanical response during the natural ageing.