Age hardening of a sintered Al–Cu–Mg–Si–(Sn) alloy

The age hardening response of a sintered Al–3.8 wt% Cu–1.0 wt% Mg–0.70 wt% Si alloy with and without 0.1 wt% Sn was investigated. The sequence of precipitation was characterised using transmission electron microscopy. The ageing response of the sintered Al–Cu–Mg–Si–(Sn) alloy is similar to that of cognate wrought 2xxx series alloys. Peak hardness was associated with a fine, uniform dispersion of lath shaped precipitates, believed to be either the β″or Q′ phase, oriented along 〈0 1 0〉α directions and θ′ plates lying on {0 0 1}α planes. Natural ageing also resulted in comparable behaviour to that observed in wrought alloys. Porosity in the powder metallurgy alloys did not significantly affect the kinetics of precipitation during artificial ageing. Trace levels of tin, used to aid sintering, slightly reduced the hardening response of the alloy. However, this was compensated for by significant improvements in density and hardness.