Effect of zinc and zirconium on the microstructure, mechanical properties and corrosion resistance of Mg-xZn-yZr-1Y alloys for biomedical applications

Six new Mg-xZn-yZr-1Y alloys were developed with variations in Zn (1, 3, 5 wt%) and Zr (0.25, 0.5, 0.75, 1 wt%) content. The alloy with 3 wt% Zn and 0.5 wt% Zr exhibited the most favourable properties including fine-grain microstructure, superior mechanical performance and enhanced corrosion resistance. This alloy achieved a tensile strength of 201.6 MPa, a yield strength of 80.7 MPa, and a Young’s modulus of 40.4 GPa, with an 11.8% elongation. Corrosion behaviour evaluated through open circuit potential, potentiodynamic polarization, and hydrogen evolution tests, confirmed its excellent corrosion resistance with a corrosion current density of 1.77 µA/cm² and a minimal hydrogen evolution rate (HER) of 0.017 ml·cm⁻²·hr⁻¹. Increasing the zinc content enhanced the tensile strength but caused a decline in ductility when exceeding 3 wt% attributed to the formation of coarse intermetallic phases. In contrast, higher Zr additions refined the grain structure and improved corrosion resistance particularly at 0.5–1 wt%. The findings underscore the crucial role of Zn and Zr in refining the grain structure and enhancing the overall properties of magnesium alloys for biomedical applications.