The effect of Zn on the age hardening response in an Al–Mg–Si alloy

Abstract Enhancing the age hardening response in Al–Mg–Si alloys during paint-bake cycle has become a research focus in automotive industry. In this study, an improvement of age hardening response can be achieved by Zn additions. The age hardness increment approaches 10HV in an Al–Mg–Si alloy containing 3.0 wt.% Zn when aged at 170 °C for 20 min, while in an Al–Mg–Si alloy containing 0.5 wt.% Zn, the hardness slightly decreases after aging. The analysis of microstructures through TEM shows that the improvement of age hardening response caused by high amount of Zn additions is attributed to the precipitations of GP (II)-zones of η-MgZn 2 and η′ phases. The effect of Zn additions on the precipitation behavior of the metastable hardening phase of Mg 2 Si (β″) at different aging temperature is investigated as well in this study.