Effects of Er Content on Microstructure and Corrosion Resistance of AM50 Alloy for Automotive Engine

AM50 alloy for automobile engine was microalloyed by addition of Er. The effects of Er content on microstructure and corrosion resistance of AM50 alloy were studied through scanning electron microscopy (SEM), X-ray diffraction (XRD), immersion test and electrochemical test. The results show that the Er-microalloyed AM50 alloy contained phases of α-Mg, β-Mg₁₇Al₁₂, Al₇ErMn₅ and Al₃Er. With the increase of Er content, the corrosion rate of the alloy first decreased and then increased in general, but the tensile strength increased first and then decreased, and the strength loss displayed the same tendency with the corrosion rate. The AM50 alloy had the best corrosion resistance and tensile properties when the addition of Er was 0.5% (mass).