Low addition of Er and Zn into biomedical magnesium with enhanced integrated properties for orthopedic applications: in vitro and in vivo studies

As the common alloying elements of Mg, rare earth elements (REEs) have been extensively explored due to their prominent effect on melt purification and mechanical strengthening. However, as for orthopedic applications, the only Mg-RE based implant that has received CE mark approval to date is developed from WE43 alloy, which contains substantial amount of REEs (4 wt% Y and 3 wt% mischmetal) and thus elicited biosafety concerns. Future advancement in novel Mg-RE based alloys is expected to reduce the amount of REEs along with its species. In this study, low amount of Er and Zn (≤3 wt%) were added into Mg. It came out that the addition of Er facilitated grain refinement while Zn contributed to the dynamic recrystallization of alloys. Compared to binary Mg-Er and Mg-Zn alloys, co-addition of Er and Zn could further strengthen the alloys. Among the alloys studied, Mg-1Er-1Zn alloy showed outstanding integrated performance, with relatively uniform corrosion pattern, superior mechanical properties and excellent osteogenic properties, indicating its potential for orthopedic applications. In light of these findings, it is recommended that optimized microstructure regulation and strict control on REEs addition be considered as crucial strategies for further development of novel Mg-RE-Zn alloys as orthopedic implants.