Effects of Zn Content on Microstructure and Intergranular Corrosion of Al-Mg-Si Alloy

The effects of 0.2wt% Zn addition on microstructure, age hardening and IGC properties of Al-Mg-Si alloy were investigated by scanning electron microscope（SEM）, transmission electron microscope（TEM） hardness testing and electrochemistry testing. The results show that the peak hardness of the alloy with 0.2wt% Zn content is 125.8 HV. Compared with 0.05wt% Zn content alloy, the hardness increases by 12.7 HV. With the addition of 0.2wt% Zn, the PFZ of the alloy becomes wider and the grain boundary precipitation phase size increases slightly, which result in the decrease of the intergranular corrosion resistance of Al-Mg-Si alloys. The corrosion current density of the alloy with 0.2wt% Zn content in the peak aging state is higher than that of the alloy with 0.05wt% Zn content.