The effect of Zn content on the microstructure and mechanical properties of the Al-mg-Si alloy.

In the present study, the influence of Zn content on the microstructure and mechanical properties of the Al-Mg-Si alloy is systematically investigated. The results show that the precipitation sequence within the grains of the alloy does not change when Zn content does not exceed 2.0 wt%. The intragranular precipitates are mainly composed of β" precipitates with a small amount of η' precipitates when Zn content reaches 4.0 wt.%. Zn addition does not affect the precipitation sequence along the grain boundaries of the alloy when Zn content does not exceed 1.0 wt.%. But the grain boundary precipitates (GBPs) transform into Zn-rich phases when Zn content increases to 2.0 wt.%. The strength of the alloy firstly gradually improves and then reduces when Zn content increases to 2.0 wt.%. This is mainly due to the effect of Zn content on the distribution of the intragranular precipitates. The strength of the alloy significantly enhances again as a result of the increase of the number density of β" precipitates and the formation of η' precipitates when Zn content reaches 4.0 wt%. [Display omitted] • Zn addition promotes the precipitation behavior of the intragranular precipitates. • The size and type of the GBPs change with the variation of Zn content in the alloy. • Zn content has great effect on the PFZ width. • Zn addition improves the strength mainly due to the high number density of the intragranular precipitates. [ABSTRACT FROM AUTHOR]