Enhanced Age-Hardening by Synergistic Strengthening from Mg-Si and Mg-Zn Precipitates in Al-Mg-Si Alloy with Zn Addition

Abstract

The accelerated age-hardening response and the enhanced peak-hardness in Al-Mg-Si with Zn addition was investigated by three-dimensional atom probe and transmission electron microscopy. The results showed that Zn addition significantly increased the number density of solute aggregates by stimulating the formation of more Mg-Si precipitates and resulted in a higher Mg/Si ratio because of the formation of Mg-Zn precipitates. A synergistic strengthening from Mg-Si and Mg-Zn-(Si) solute aggregates was estimated to accelerate the age-hardening response at the early aging stage, and that from β" phases for Mg2Si system and Guinier-Preston (GP) I zones/η′ phases for MgZn2 system enhanced the peak-harness.