Preparation Of Biodegradable Zn-Mg-Zr Alloys And Its Properties Evaluation

Zinc（Zn）-based materials is expected to be a new generation of biodegradable metallic implants.Nevertheless,the mechanical properties of Zn alloys still need to be improved to meet the demands of biodegradable implants.The study showed that adding 1%magnesium（Mg）to Zn can effectively improved the strength and ductility of the as-cast Zn Mg alloys.Zirconium（Zr）as a biocompatible alloy element could effectively refine the grains of Zn alloys and improve their mechanical properties and corrosion resistance.In this study,Zn1Mg was chosen as a base alloy to improve the mechanical properties of alloys by addition of zirconium（Zr）.New ternary Zn1Mgx Zr（x=0.1～0.5）alloys were prepared by melting method to investigate the effects of Zr on the microstructure,mechanical properties,corrosion performance and biocompatibility.Forging and extrusion treatment were employed to improve the mechanical properties,regulate the corrosion properties of alloys.The results revealed that the microstructure of ZnMgZr alloys were consisted of Zn primary dendrite,eutectic mixtures of Zn and Mg₂Zn₁₁,and second phase particles Zn₂₂Zr.The addition of Zr refined the microstructure of the as cast ZnMgZr alloys.The finer microstructure accordingly improved the mechanical properties and the corrosion resistance of the alloys.The ultimate tensile strength（UTS）and the elongation increased from 75 MPa and 0.5%for Zn1Mg to 108.0 MPa and 1.0%for Zn1Mg0.1Zr.The degradation rate of immersion decreased from0.07 mm/year for Zn1Mg to 0.059 mm/year for Zn1Mg0.1Zr.Forging and extrusion treatment homogenized the microstructure of ZnMgZr alloy,which further enhanced the mechanical and corrosion performance of the alloy.Forging process increased the UTS and the elongation to 212～237MPa and 7.2～9.5%,decreased the degradation rate of immersion to 0.051～0.054mm/year.Extrusion process increased the UTS and the elongation to 322～332MPa and 2.9～3.3%,decreased the degradation rate of immersion to0.040～0.045mm/year.In this study the HUEVC cell proliferation rate of 25%extract for all Zn1Mgx Zr alloy after cultured for 1,3,7 days was more than 75%,and the hemolysis rate was lower than 3%,which meets the requirements of biomedical materials for cytotoxicity and hemolysis rate.