Effect of cerium addition on microstructure and corrosion resistance of die cast AZ91 magnesium alloy

A novel AZ91 Ce containing magnesium alloy characterized by excellent corrosion resistance is fabricated by adding rare earth Ce (cerium) in the form of a Mg-Ce master alloy. The metallographic investigation shows that Ce added to AZ91 can obviously decrease the size of beta-Mg17Al12 and forms Al11Ce3 intermetallic compounds in the shape of fine needles. The corrosion tests and electrochemical measurements indicate that the corrosion resistance of AZ91 Cc containing magnesium alloy is obviously higher than that of AZ91. Furthermore, increasing the content of Cc in the magnesium alloy can further enhance the corrosion resistance. X-ray photoelectron spectroscopy (XPS) reveals that Ce can be incorporated into corrosion products in the form of CeO2 in the course of corrosion. Based on the preliminary analysis, the addition of Cc can improve the corrosion resistance of AZ91 by decreasing the size of beta-Mg17Al(12) and enhancing the protective effectiveness of corrosion products.