The Development Of New Magnesium Alloy And Its Modified Coating As Biomaterial

Recently, magnesium and magnesium alloys have gained widespread attention asa potential biodegradable orthopedic material due to its non-toxic nature andbiocompatibility, its mechanical compatibility with bone, and its degradability inhuman body fluids. Nevertheless, in physiologic fluid which is rich in chlorine,magnesium alloys are corroded so fast that they lose their mechanical integrity beforethe broken bone is healed. Therefore, it becomes one of the key issues for magnesiumalloys in biomaterial applications to improve their corrosion property in physiologicenvironment. Element alloying is one of the effective ways to improve their corrosionperformance. In this paper, Zr, Ca, Sr and Sn as alloying elements were added to themagnesium. New Mg-Zr, Mg-Zr-Ca, Mg-Zr-Ca-Sr-Sn alloys were fabricated.Cathodic polarization on Mg-Zr-Ca-Sr-Sn alloy was carried out in0.1MMg（NO₃）₂·6H₂O aqueous solution at room temperature to form Mg（OH）₂thin film onthe magnesium matrix. Then, TiO2thin film was fabricated on Mg（OH）₂film using thesol-gel method. Then, the microstructure observation, electrochemical measurementsand immersion tests were used to characterise the property of the alloys.The results indicated that the Mg-Zr consisted of Mg and single phase Zr. Theadding of Zr could effectively adjust the mechanical performance of the magnesium.Mg-Zr-Ca alloy was mainly composed of Mg and Mg2Ca. Furthermore, the Mg2Caphase was mainly in the grain boundary. The electrochemical result indicated thatMg-Zr-Ca had good corrosion resistance in SBF. Immersion testes indicated the maincorrosion production was the Mg（OH）₂, with small quantity of HA. Themicrostructure was different with different amounts of Sr and Sn added into theMg-Zr-Ca alloy. It was found that there was a new phase Mg2Sn formed in the graininterior. With more Sr and Sn added into the magnesium, the new Mg2Sn phaseincreased. The electrochemical and immersion tests indicated that the Mg2Sn caneffectively modify the corrosion performance of the magnesium in SBF, and TiO2thinfilm had good protective function to the magnesium alloy matrix. It can raise the Ecorrand decrease the Icorreffectively.