Mechanical and corrosion properties of extruded Mg–Zr–Sr alloys for biodegradable implant applications

Magnesium (Mg) alloys have been extensively studied for their potential application as biodegradable implants. Zirconium (Zr) and strontium (Sr) are some of the few elements that are considered both biocompatible and biofunctional. In this study, extrusion was performed on Mg–Zr–Sr alloys in order to further improve their mechanical and corrosion properties and to clarify the effects of Zr and Sr additions on the materials properties of Mg alloys. Results indicated that in the extruded Mg–Zr–Sr alloys, the intermetallic Mg17Sr2 phases were accumulated at the grain boundaries, which triggered particle-stimulated nucleation, leading to reduced grain size and deformation twining. Increasing Zr content from 0.5 wt% to 3 wt% in the extruded Mg–xZr–1Sr (x = 0.5–3 wt%) alloys resulted in an increase of 25.4% in elongation and 5.9% in ultimate tensile strength. On the other hand, increasing Sr content from 1 wt% to 3 wt% in Mg–0.5Zr–xSr (x = 1–3 wt%) alloys improved only the tensile strength by 19.3% and the highest ultimate strength of 302 MPa was observed in extruded Mg–0.5Zr–3Sr. The tensile yield strength of extruded Mg–xZr–ySr (x = 0.035–3 wt%; y = 0.2–3 wt%) alloys ranged from 210 to 275 MPa. Compressive strength and strain of extruded Mg–Zr–Sr alloys ranged from 289 to 368 MPa and from 11.0% to 18.9%, respectively. The corrosion rates of the extruded Mg–Zr–Sr alloys ranged from 4.6 to 10.7 mm y−1 from potentiodynamic polarization tests. Overall, the extruded Mg–0.5Zr–3Sr showed optimum mechanical and corrosion properties and can be considered a promising biodegradable implant material.