Effect of Zn Content on the Microstructure and Corrosion Behaviour of Mg-7Y-0.6Zr Alloy

Mg-7Y-0.6Zr-xZn (x = 0, 0.5, 1.0, 1.5, 2.0, 2.5, wt.%) alloys were prepared by the metal mould casting method. Effect of Zn content on the microstructures and corrosion behaviour were investigated. Results showed that microstructures were refined and volume fraction of secondary phase Mg24(YZn)5 was increased with increasing addition of Zn element. Results of electrochemical tests demonstrated that the corrosion potential of Mg-7Y-0.6Zr alloy was about -1.77 V, and, with addition of 0.5~2.0 wt.% Zn element, corrosion potential moved to more positive values than that of Mg-7Y-0.6Zr alloy. Mg-7Y-0.6Zr-0.5Zn alloy possessed the most positive corrosion potential of -1.53 V. The results of immersion test with different time also indicated that corrosion rate could be decreased by addition of 0.5~2.0 wt.% Zn, and Mg-7Y-0.6Zr-0.5Zn alloy exhibited the lowest corrosion rate.