Microstructure and corrosion behavior of Mg–Zn–Y–Al alloys with long-period stacking ordered structures

Mg97−xZn1Y2Alx alloys with long-period stacking ordered (LPSO) structures were prepared by conventional casting method. The optical microscopy (OM), X-ray diffraction (XRD) and the scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) were used to analyze the microstructure of the alloys with different compositions. Immersion test and electrochemical measurement were used to evaluate the corrosion behavior of the alloys at room temperature, and the corrosive medium is 3.5% NaCl aqueous solution. The results showed that, with the increasing aluminum (Al) addition, except α-Mg and LPSO phases, new phases also emerged on the grain boundaries. At the same time, the zigzag part of LPSO phases disappeared, and the boundaries between LPSO phases and α-Mg became smooth. Furthermore, the addition of Al to Mg–Zn–Y alloys could hinder the activity of cathodic hydrogen evolution reaction and improve the uniformity and compactness of the protective surface film, thus, enhanced the corrosion resistance of Mg–Zn–Y alloys.