Influence of Gd and Ca on microstructure, mechanical and corrosion properties of Mg-Gd-Zn(-Ca) alloys

Microstructures, mechanical and corrosion properties of the Mg-xGd-1Zn (x=3, 6, and 9 wt%) and Mg-9Gd-1Zn-yCa (y=0, 0.2, and 0.6 wt%) alloys were studied and compared for biomedical applications. The results show that the microstructures of the alloys are composed of primary -Mg, eutectic phase, lamellar long period stacking ordered (LPSO) phase, and MgxGd compounds. The grain size is apparently refined and the volume fraction of the eutectic phase increases with increasing Gd. The grain size is not reduced and the divorced eutectic phase is formed with Ca addition. Gd plays a more positive role in the improvement of yield strength while Ca shows a higher enhancement on microhardness. The higher Gd addition results in worse corrosion resistance of the Mg-xGd-1Zn alloy, nevertheless, the alloy with 0.6 wt%Ca has the best corrosion resistance among the Mg-9Gd-1Zn-yCa alloys. The as-cast Mg-3Gd-1Zn alloy exhibits the lowest corrosion rate, and is a promising alloy for biodegradable applications.