Study On The Bio-corrosion Behavior Of Mg-Zn Alloys

Due to their high specific strength,good biocompatibility and biodegradability,Mg alloys have aroused the interest of many biological materials researchers.In this thesis,Mg,Mg-0.3Mn,Mg-1Zn-0.3Mn,Mg-2Zn-0.3Mn,Mg-4Zn-0.3Mn and Mg-6Zn-0.3Mn alloys were prepared by vacuum melting and extrusion.X-ray diffraction analysis,optical microscopy,scanning electron microscopy,tensile test,immersion test,electrochemical test and cyclic stress corrosion test were carried out to study the microstructure and mechanical properties of Mg alloy.The role of Mg-Zn second phase in cathodic activation during corrosion process of Mg alloys,and the effect of cyclic tensile stress on the corrosion resistance of Mg alloys and the possible corrosion mechanism were discussed.The results are as follows:Static corrosion test results show that,the corrosion resistance as-cast Mg-Zn alloys decreased gradually with the increase of Zn content.The corrosion rate of the as-extruded alloys is in the following order,Mg-0.3Mn>Mg-1Zn-0.3Mn>Mg-2Zn-0.3Mn>Mg-4Zn-0.3Mn>Mg-6Zn-0.3Mn>Mg,with the increase of Zn content,the corrosion resistance decreases,since the Mg-Zn phase can form galvanic corrosion with the Mg matrix to promote the corrosion of the Mg alloys.Corrosion resistance decreases with the increase of corrosion time during the corrosion process of Mg alloys due to the cathodic activation behavior.We found that the cathodic activation behavior is mainly caused by the impurity elements,and the Mg-Zn phases do not contribute to this.The results of cyclic tensile stress corrosion tests show that the static corrosion resistances of pure Mg and Mg-1Zn are better than that of dynamic corrosion after cyclic loading,and the corrosion resistance decreases with the increase of applied stress.After the cyclic stress was applied,stable oxide film formed gradually on the surface of the pure Mg specimens with the increase of time,and its corrosion resistance began to get better and remained stable.However,with the increase of time,there will still be pitting on the surface of Mg-1Zn under cyclic tensile stress,but at the same time surface oxide film is also formed,and then the formation of pitting corrosion and oxide film will form a dynamic balance.