Preparation And Properties Of Biomedical Degradable Zn-Mg Based Alloys

Biological metal materials are widely used in medical field because of their good processability and mechanical properties.As a kind of medical implant material,biodegradable metal materials are expected to solve the problem that traditional metal biomaterials such as titanium alloys,medical stainless steels,and cobalt-based alloys require secondary surgery removal due to good corrosion resistance,so they have certain advantages.Among biodegradable metal materials,zinc alloys have a wide range of applications because of their good biocompatibility.However,pure zinc has poor mechanical properties and a relatively slow degradation rate,which limits its application in the biomedical field.Therefore,improving the mechanical properties of zinc-based alloys,regulating the corrosion and degradation rates of zinc-based alloys,and effectively improving their antibacterial properties are the main research goals of this paper.In this study,Zn-Mg binary alloys were prepared by powder metallurgy method.The effects of pressing pressure,sintering temperature,and Mg contents on the porosity,microstructure,mechanical properties,and corrosion properties of the Zn-Mg alloys were studied.Based on Zn-Mg alloys,Cu and Ag elements were added to prepare Zn-Mg-Cu and Zn-Mg-Ag ternary alloys,respectively.The effects of Cu and Ag elements on microstructure,mechanical properties,corrosion resistance and antibacterial properties of Zn alloys were studied.The research results of Zn-Mg alloys show that with the increase of pressing pressure and sintering temperature,the porosity of Zn-Mg alloys decreases.When the Mg content increases from 0.5wt%to 2.5wt%,the porosity of the Zn-Mg alloys decreases first and then increases.The porosity of the Zn-1Mg alloys was the lowest value.SEM and XRD analysis results show that only?-Zn solid solution exists in the Zn-Mg alloys when the Mg contents are 0.5?2.0wt.%,but the Zn-2.5Mg alloys have a second phase of Mg₂Zn₁₁.With the increase of sintering temperature and Mg contents,the microhardness and compressive strength of Zn-Mg alloys increase.The maximum microhardness and compressive strength of Zn-2.5Mg alloy are 65.8HV and 112.4MPa after sintered at 380?for 2h.Electrochemical analysis and corrosion weight loss experiments show that Zn-Mg alloys exhibit better corrosion resistance than pure Zn with 0.5wt%and 1.0 wt.%Mg.The Zn-1.0Mg alloys have the most corrosion resistance.When the Mg contents are 1.0?2.5wt%,with the increase of the Mg contents,the self corrosion potential of Zn-Mg alloys decreases,but passivation current density,corrosion rate and weight loss of Zn-Mg alloys all increase which shows corrosion tendency of Zn-Mg alloys is higher than pure Zn.The research results of Zn-Mg-Cu alloys shows that Zn-2Mg-x Cu alloy(x=0.5?2.0wt%)all have?-Zn and Mg₂Zn₁₁ phases.With the increase of Cu contents,the porosity and contents of Mg₂Zn₁₁ phase increase,but the microhardness and compressive strength of the Zn-2Mg-x Cu alloy first increase and then decrease.The microhardness and compressive strength of Zn-2Mg-1.5Cu alloy sintered at 380?for 2h come to the maximum of 77.3HV and 126.7MPa.When increasing the Cu contents,the passivation current density,corrosion rate and weight loss of Zn-Mg-Cu alloys all incease which shows Zn-Mg-Cu alloys have higher corrosion tendency than Zn-Mg alloys.After immersed in artificial simulated body fluid for 14 days,obvious corrosion pits appears on the surface of the alloys.The results of corrosion products show that the corrosion of the Zn-Mg-Cu alloys in SBF environment can help guide calcium phosphate deposition.The study of Zn-Mg-Ag alloy shows that after the addition of Ag element in the Zn-Mg matrix(x=0.5?2.0wt%),the second phase of Mg Zn₂ appears.With the increase of the Ag contents,the content of Mg Zn₂ phase increases.The microhardness and compressive strength of sintered Zn-2Mg-x Ag alloys first increase and then decrease.When the Ag content is1.5wt%,the microhardness and compressive strength of Zn-2Mg-1.5Ag sintered at 380?for2h reach the maximum of 81.9HV and 130.6MPa.Compared with Zn-Mg and Zn-Mg-Cu alloys,the self-corrosion potentials of the Zn-Mg-Ag alloys are not significantly different,but the passivation current density,corrosion rate and weight loss significantly increase.After immersed in artificial simulated body fluid for 14 days,obvious corrosion pits appears on the surface of the Zn-2Mg-x Ag alloys.The corrosion products have P and Ca elements.The results of antibacterial performance research on Zn-Mg-Cu alloys and Zn-Mg-Ag allosy show that the two kind of ternary alloys have good killing and inhibiting effects on Staphylococcus aureus and Escherichia coli,and they have good antibacterial properties.The diameter of the bacteriostatic circle of Zn-Mg-Ag alloy is larger than that of Zn-Mg-Cu alloy,and the absorbance value of co-culture with Zn-Mg-Ag and bacteria is small,which proves that Zn-Mg-Ag alloy has better antibacterial performance than Zn-Mg-Cu alloy.