Study On The Microstructure And Properties Of Novel Biodegradable Zn-Sn And Zn-Zr Alloys

Over the past two decades,biodegradable materials have attracted significant attentions because of their promising applications such as bone implantation and intravascular stent.Mg/ Mg alloys and Fe/ Fe alloys,as biodegradable materials,have been comprehensively investigated for temporary implants.It was found that Mg/ Mg alloys were corroded rapidly in the physiological environment.On contrary corrosion rate of Fe/ Fe alloys is lower than the clinical needs so would stay longer time in human body even after finishing the healing process.Zn as another used biodegradable material shows ideal corrosion behavior in biological environment.However,the mechanical properties of pure Zn is poor and cannot meet the required properties of the implants.Therefore,there are considerable demands for the development of Zn.Herein in order to improve the mechanical properties of pure Zn,a series of as-extruded Zn-Sn and Zn-Zr alloys were fabricated and their microstructure,phase composition,mechanical properties,corrosion behavior,corrosion mechanism and biocompatibility were investigated in detail.Zn-Sn alloys with nominal compositions of Zn-0.9Sn,Zn-1.4Sn and Zn-1.9Sn(wt.%)were prepared.Zn and Sn did not form a solid solution or an intermediate phase.Compared with pure Zn,the tensile strength,yield strength and elongation of Zn-Sn alloy have been increased by 21.3%,29.9% and 68.6%,respectively.The corrosion resistance of Zn-Sn alloys increases with the increase of Sn content,the corrosion resistance of Zn-1.9Sn is the best,and the degradation rate is only 0.08 mm/y.The biocompatibility evaluation results indicated that ZnSn alloys show desirable blood compatibility,but the cell compatibility is not good,and it can cause cell toxicity.Besides,Zn-Zr alloys with nominal compositions of Zn-0.5Zr,Zn-0.8Zr and Zn-1.1Zr(wt.%)were prepared.Zn and Zr can form an intermediate phase Zn2 Zr,which mainly exists in the Zr rich phase.Obtained results demonstrated that the tensile strength,yield strength and elongation of Zn-Zr alloy in compare with pure Zn were increased by 69.9%,54.6% and 19.6%,respectively.Also,the corrosion resistance of Zn-Zr alloy increases with the increase of Zr content,so that the corrosion resistance of Zn-1.1Zr and Zn-0.8Zr are relatively good.Generally,it was determined that compared with Zn-Sn alloys,Zn-Zr alloys show better blood compatibility and cell compatibility.In addition,cytotoxicity test results indicated that it is non-toxic to cells,and even promote cell growth.Briefly,due to superior strength,high corrosion resistance and adequate degradation rate,Zn-Zr alloys have potential to replace the reported biodegradable implant materials and Zn-0.8Zr is the best choice.