| In recent years,with the alloying of magnesium,magnesium alloys have been widely used as biomaterials,which mainly depend on the excellent properties of magnesium alloys.The specific strength and specific stiffness of magnesium alloys are relatively high,and they are similar to human bone density.It is widely used in the field of cardiovascular stents because of its biocompatibility,light weight and low cost.However,magnesium alloys as medical materials have not fully met the mechanical properties,corrosion properties and biocompatibility required for cardiovascular stents,which makes them not widely used in clinical practice.Therefore,further research on magnesium alloys is needed to achieve the conditions for cardiovascular stent applications.Based on the research group,the as-cast Mg-2Y-1Zn-0.4Zr biomagnesium alloy with good comprehensive performance was selected.The hot extrusion deformation treatment was carried out,and the mechanical properties and corrosion performance tests were carried out by designing different extrusion processes.Preferably,the optimum extrusion process is preferred.The wrought magnesium alloy,which preferably exhibits the optimum extrusion process,is then heat treated to further optimize alloy properties by heat treatment.The heat treatment methods used in this paper are mainly aging treatment and annealing treatment.Organization and performance testing methods are: OM,SEM & EDS,XRD,ISCM test,room temperature stretching,weight loss test,hydrogenevolution test and electrochemical test.The organization analysis,mechanical properties and corrosion performance test laid the foundation for the next alloy biocompatibility test.After extrusion deformation,the microstructure and properties of the alloy change significantly.The grain of the alloy is remarkably refined,and the second phase is crushed.Some of them are banded or clustered,and some are dissolved in the matrix.However,the second phase has not changed,but the morphology and distribution have changed.The large grain refinement and the change of the second phase distribution and morphology greatly optimize the mechanical properties of the alloy.The mechanical properties of the alloy are increased from the as-cast tensile strength 242 MPa,the yield strength 135 MPa and the elongation 14.4% to the tensile strength after extrusion.327 MPa,yield strength 322 MPa and elongation 24.9%.At the same time,the corrosion performance of the alloy after extrusion was tested.The test results show that the alloy has the best corrosion resistance when the extrusion process is 300 ° C& 60 mm / min.After extrusion deformation treatment,residual stress and high density misalignment exist inside the alloy,and the grain size of the alloy is not uniform.The heat treatment can effectively eliminate the internal residual stress of the alloy and reduce the dislocation density,and at the same time make the grain size more uniform and full.Through heat treatment,the alloy structure is optimized,and the mechanical properties of the alloy are also improved.After immediate treatment(200 ° C + 12 h),the alloy properties reach tensile strength326 MPa,yield strength 317 MPa and elongation 37.1%,and annealing temperature 380 ° C alloy.The properties were tensile strength 352 MPa,yield strength 349 MPa,and elongation 31.3%.In this paper,the as-cast Mg-2Y-1Zn-0.4Zr bio-magnesium alloy is extruded to make the grain refinement and promote the second phase refinementand solid solution into the matrix,thus greatly optimizing the alloy properties.In addition,the different process heat treatment of the extruded alloy can further optimize the alloy structure to enhance the properties of the alloy on the basis of extrusion,so that the magnesium alloy can be applied to clinical medicine more quickly. |
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