Microstructure, mechanical and corrosion properties of Mg-Zn-Sr-Ca alloys for use as potential biodegradable implant materials

Effects of Ca addition on as-cast microstructure, mechanical and corrosion properties of Mg-2Zn-0.3Sr alloy were investigated for biodegradable implant application. First, a comparison between Ca and Sr addition in Mg-2Zn alloy was studied. Mg-2Zn-0.3Sr showed the better corrosion performance, but the worse mechanical property. Then, the results of Ca addition indicated that the dendritic phases dispersed in the Mg matrix. The grains became smaller as Ca content increased. The ultimate tensile strength of Mg-2Zn-0.3Sr-0.3Ca alloy was strengthened to about 170MPa, along with a good ductility of 10%, due to the refinement of grains and homogenous morphology. The ternary alloy had the lowest degradation rate. Mg-2Zn-0.3Sr-0.3Ca still presented a considerable corrosion resistance. 0.5wt% Ca addition brought more and coarser second phases, and worse mechanical and corrosion property. It is suggested that minor addition of Ca (0.1-0.3wt%) in Mg-2Zn-0.3Sr alloy would benefit the practical performance for use in biodegradable implants.