Microstructures and corrosion behavior of biodegradable Mg-6Gd-xZn-0.4Zr alloys with and without long period stacking ordered structure

The microstructures and corrosion behavior of Mg-6Gd-xZn-0.4Zr (x = 0.5, 1, and 2 wt%) alloys under as-cast and solution treated conditions were studied. Long period stacking ordered (LPSO) structure formed in the as-cast alloys and disappeared after solution treatment. The distribution of LPSO structure is related to Zn concentration. The corrosion rates of the as-cast and solution treated alloys increased with increasing Zn content. The as-cast alloys, which had LPSO structure located at the outer edges of grains, exhibited better corrosion resistance and a more uniform corrosion mode as compared to the alloy which had LPSO structure distributed throughout some whole grains.