Corrosive wear resistance of Mg-Al-Zn alloys with alloyed yttrium

In this study, Mg-3Al-1Zn alloys containing small amounts of yttrium (<4 wt%) were prepared using an induction furnace. The corrosion resistance of as-cast alloys in a 3.5% NaCl solution was investigated by electrochemical polarization testing and their corrosive wear resistances in the same solution were evaluated using a pin-on-disc tester. Microstructures and worn surfaces of the alloys were examined using scanning electron microscopy. It was demonstrated that that adding yttrium in Mg-3Al-1Zn alloy introduced Al2Y precipitates and minimized the precipitation of Mg17Al12 phase with refined microstructure. The wear resistance of Mg-3Al-1Zn alloy was improved when yttrium was added due to the formation of uniformly distributed finer and harder Al2Y precipitates. The yttrium addition to Mg-3Al-1Zn alloy also enhanced the corrosion resistance, since the galvanic effect of finer and dispersed Al2Y precipitates was weaker than that of the coarse Mg17Al12 particles and their network. The combination of improved strength and corrosion resistance resulting from the Y addition increased the corrosive wear resistance of the material. (C) 2013 Elsevier B.V. All rights reserved.