Research On The Preparation And Degradability Of The Medical Zinc Alloy Wire

In recent years,degradable implant(human body)materials have received extensive attention from clinical medicine and biomaterials science circles.The degradable human implant materials currently being developed by the academic community are mainly iron-based,magnesium-based and zinc-based alloys.Existing research results show that the degradation rate of ferroalloy materials is too slow in the physiological environment of the human body,while the degradation rate of magnesium alloy materials is too fast and cannot be uniformly corroded,so the clinical application is greatly restricted.Compared with iron-based and magnesium-based alloys,zinc alloys have moderate corrosion rates and better mechanical properties,and are regarded as implantable metal materials with more application prospects by the biomedical community.However,the mechanical strength of pure zinc is low,and its comprehensive mechanical properties must be improved through alloying technology and optimized processing technology to meet the requirements of clinical applications.This paper uses a variety of macro and micro analysis methods to systematically study the microstructure of pure Zn and Zn-0.5Cu,Zn-0.5Cu-0.5Ca and Zn-0.5Cu-0.5Ca-0.5Fe alloys in various states,mechanical properties and in vitro degradation properties in solution,as well as the effect of heat treatment on alloy structure and properties.The focus is on the plastic deformation mechanism of pure zinc and zinc alloy in the process of drawing cumulative deformation,as well as the deformation softening and cold deformation texture evolution behavior.The research results show that a small amount of Cu,Ca,Fe alloying can promote the refinement of the zinc alloy structure.The structure of as-cast Zn-0.5Cu alloy is composed of matrix phase and a small amount of second phase.Adding a small amount of Ca on the basis of Zn-0.5Cu alloy or adding Ca and Fe at the same time will cause coarse Ca Zn₁₃ second phase or both Ca Zn₁₃ and Fe Zn₁₃ second phase particles to appear in the microstructure.The addition of a small amount of Cu,Ca,Fe all significantly improved the strength and hardness of the alloy.During the hot extrusion process,both pure zinc and zinc alloy undergo dynamic recrystallization,and the strength and plasticity are significantly improved.During the multi-pass cold drawing deformation process,both pure zinc and zinc alloy will undergo dynamic recrystallization,causing the alloy to harden first and then"soften".When the cumulative deformation of the Zn-0.5Cu alloy during cold drawing reaches 99%,the grains of the matrix phase in the microstructure are refined to ultra-fine grains between 100-200nm,and the tensile strength and hardness are reduced to 78±1MPa and 38±1HV,equivalent to 35%and 50%of the highest value of strength and hardness when the drawing deformation is 30%The heat treatment of the Zn-0.5Cu wire with the alloy cold drawn to?=0.2mm found that with the increase of the heat treatment temperature,the grains of the Zn-0.5Cu alloy wire gradually grew into regular equiaxed crystals,and the grain boundaries It becomes clear gradually,and the precipitated phase gradually dissolves.After heat treatment,the strength and hardness of the alloy increase significantly,and the elongation decreases slightly.The Zn-0.5Cu alloy is annealed at 250?for 5 minutes,and the tensile strength and elongation of the wire are154±3MPa and 45.3±5.5%,which has good comprehensive mechanical properties.The extruded pure zinc and zinc alloy form a typical{0001}//ED base fiber texture,and the orientation of the microtexture is concentrated in{0001}<11(?)0>and{0001}<10(?)0>,Zn-0.5 The texture density of Cu and Zn-0.5Cu-0.5Ca-0.5Fe after extrusion is stronger than that of pure zinc.The large deformation during the drawing process induces the recrystallization process,the twin crystals in the pure zinc and Zn-0.5Cu crystals disappear,the fiber texture of the basal surface disappears,and the basal surface is perpendicular to the extrusion direction,forming a<0001>//ED texture Structure.With further drawing,the slip systems of the basal,prismatic,and conical surfaces of the grains all start,and the grain texture type changes again.Compared with pure zinc,the degradation rate of extruded zinc alloy wire in Hank's solution and 0.9%Na Cl solution increases after alloying with Cu,Ca,and Fe.The degradation performance of Zn-0.5Cu alloy during the entire immersion period is better than that of Zn-0.5Cu-0.5Ca and Zn-0.5Cu-0.5Ca-0.5Fe alloys.As the degradation progresses,the surface of the sample will be covered with a layer of degradation products,which slows down the corrosion process.The addition of Ca and Fe makes the deposited film more stable.In the late stage of degradation,the corrosion product layer falls off,and the alloy degradation rate increases again.The 28-day immersion weight loss test showed that the degradation rates of Zn-0.5Cu,Zn-0.5Cu-0.5Ca and Zn-0.5Cu-0.5Ca-0.5Fe zinc alloys in 0.9%Na Cl solution were0.39mm/year and 0.32/Year and 0.36/year,in Hank's solution,they were 0.14mm/year,0.12mm/year and 0.12mm/year,respectively.After further cold drawing cumulative deformation to 65%and 99%,the alloy structure is refined and uniform,resulting in the improvement of the corrosion resistance of the alloy.