Effects Of Low Content Zinc And Zirconium On Microstructures And Properties Of Medical Magnesium Alloys

The demand for biomedical materials and their products is growing with the development of modern science and technology as well as people's attention to medical and health issues.Research and development of biomedical materials are very important for the development of the national economy and people's health.Due to its degradability and excellent biocompatibility magnesium alloy is expected to be used in implanted medical devices that do not need to exist in the body for a long time.However,its application is limited due to the surrounding environment changes too quickly and mechanical properties are lost too fast caused by raid degradation and local degradation.The mechanical properties and corrosion behavior of magnesium alloys can be improved by adjusting alloying elements and content and plastic working.In this paper,the Mg-Zn-based alloys contain low zinc and low zirconium were researched.X-ray diffraction,optical microscopy,scanning electron microscopy,immersion experiments and electrochemical experiments were used as analytical methods.The influence of Zn content on microstructure,mechanical properties and corrosion properties of as-cast and extruded Mg-Zn alloy and the influence of Zr content on the microstructure,mechanical properties and corrosion properties of as-cast and extruded Mg-Zn-based alloys were analyzed systematically and the mechanism of the changes was explored.Cell biological tests were performed on magnesium alloys with different Zn and Zr contents,and the effects of Zn and Zr elements on the biocompatibility of magnesium alloys were simply explored.The aim is to design low-alloyed magnesium alloys with good mechanical properties,corrosion properties and biocompatibility,which provides the research foundation for the design of magnesium alloy.The microstructures of the as-cast and extruded Mg-XZn(X=1.5,3,4)binary alloys were single phases.As the Zn content increased,the grain size of the as-cast alloy decreased slightly,no significant change appeared in grain size of as-extruded alloy.As the Zn content increased,the tensile strength of the binary alloy increased,but the elongation decreased slightly.The corrosion morphology of the three alloys all showed a porous structure.The corrosion resistance of the as-cast alloy increased first and then decreased with the increase of Zn content,while the corrosion resistance of the extruded alloy decreased with the increase of Zn content.Dynamic recrystallization occured after extrusion,the grains were significantly refined,and the comprehensive mechanical properties of three alloys were significantly improved.Meanwhile,the grain boundaries increased after extrusion,corrosion was more likely to occur,and corrosion resistance was reduced.After adding the Zr element to the magnesium-zinc binary alloy,the grains of alloy were significantly refined,and the mechanical properties and corrosion properties were dramatically improved.Under the simultaneous action of the Zn and Zr elements,with the Zn content slightly reduced,the tensile strength is slightly decreased,the elongation is slightly increased,and the corrosion resistance is greatly improved.With a slight increase of Zr content,there is little difference in grain size,both tensile strength and elongation increased,and the corrosion resistance of the as-cast alloy is improved.However,the corrosion resistance of the extruded alloys is not much different may be due to a Zr enrichment phenomenon appeard in the structure of the extruded Mg-2Zn-0.5Zr alloy.For the extruded Mg-1.5Zn,Mg-3Zn and Mg-1.5Zn-0.1Zr alloy,with the increase of Zn content,the proliferation rate of MC3T3-E1 cells increased greatly,and the number of platelet adhesion decreased slightly.With the addition of Zr elements,the MC3T3-E1 cells proliferation rate increased slightly,and the number of platelet adhesions increased significantly.Both Zn and Zr elements can promote the proliferation of bone cells,Zr element has procoagulant effect.By exploring the contents of Zn and Zr elements and the subsequent extrusion processing on the microstructure and properties of Mg-Zn-based alloys,the Mg-1.5Zn0.1Zr alloy with good comprehensive mechanical properties,corrosion resistance and biocompatibility was obtained.