Fatigue and creep deformed microstructures of aged alloys based on Al–4% Cu–0.3% Mg

The addition of 0.4 wt.% of silver or cadmium to the alloy Al–4% Cu–0.3% Mg which has a high Cu:Mg ratio, changes the nature, morphology and dispersion of the precipitates that forms on age hardening at medium temperatures such as 150–200 °C. Fatigue and creep tests were carried out on alloys aged to peak strength at 170 °C. The tensile properties of the alloys aged at 170 °C increased in the order Al–4% Cu, Al–4% Cu–0.3% Mg, Al–4% Cu–0.3% Mg–0.4% Cd, and Al–4% Cu–0.3% Mg–0.4% Ag. Despite differences in their microstructures and tensile properties, the fatigue performance of the alloys was relatively unaffected. Fatigue behaviour was similar in each case and the alloys showed identical fatigue limits. Major differences were observed in the creep performance of the alloys creep tested at 150 °C in the peak strength condition age hardened at 170 °C. Creep performance of the alloys increased in the order of their tensile properties. The purpose of the present work was to discuss the fatigue and creep deformed microstructure of these alloys.