Study On The Electroforming Process Of Biodegradable Iron-zinc Alloy

Iron-based biodegradable metal has gradually become a research hotspot of biodegradable materials due to its advantages of good mechanical properties,biocompatibility and good degradability.However,the degradation rate of iron-based biodegradable metals prepared by the existing process is slow and the clinical requirements are inconsistent.Therefore,it is the main purpose of this study to study the preparation process and improve the degradation rate.Alloying is a method that can effectively improve the degradation rate of iron-based metals.The addition of some specific alloying elements can not only improve the degradation rate of iron-based alloys,but also improve their mechanical properties.As a very mature technology,electroforming technology can deposit metal layers on complex substrates,and realize the deposition of specific functional structures by controlling various process parameters.The electroforming equipment is simple,easy to operate,low in cost,and the alloy prepared has excellent microstructure and grain morphology.Therefore,research on the preparation process and degradable mechanism of suitable degradable alloys provides a possible technical support for the production of clinical bioimplants.In this study,electrocasting was used to prepare biodegradable iron-zinc alloys.The electroforming process was optimized.The co-deposition mechanism of iron-zinc alloys was preliminarily discussed.The content of iron-zinc alloys,surface microstructure and mechanics were studied by different process parameters.In-vitro static immersion tests were carried out on various contents of iron-zinc alloys in simulated body fluids to study the degradation behavior and mechanism of iron-zinc alloys.The test results of the electroformed Fe-Zn alloy show that when the current density is low（<0.4A/dm²）,iron deposition mainly occurs and the current density increases,and the iron content in the alloy gradually approaches the iron ion content in the solution.When the p H is 4.5,the maximum deposition amount of zinc is obtained.Lowering the p H,increasing the total metal ion concentration in the solution,the iron content in the electrodeposition gradually increases,approaching a constant value.In general,iron tends to deposit at higher temperatures,lower p H and higher total metal ion concentration.The suitable temperature for iron deposition is 60℃,at this temperature,it is normal co-deposition.There is a transition current density during the co-deposition of the iron-zinc alloy.The transition current density increases with increasing temperature,decreases with increasing p H,and increases linearly with increasing total metal ion concentration.The mechanical properties of electro-cast zinc alloys（ULS>360MPa,YS>280MPa）are higher than human bones and meet the mechanical properties required as bone implants.The results of the degradation test in vitro of iron-zinc alloys indicate that the in vitro degradation rate of electroformed iron-zinc alloy is related to the amount of iron content.As the iron content increases,the degradation rate of the alloy slows down,and the overall degradation rate is higher than that of electroformed pure iron.The degradation of the iron-zinc alloy in the simulated body fluid is uniformly corroded.The corrosion begins to corrode from the surface defects of the iron-zinc alloy.But as the corrosion time increases,the corrosion products accumulate and the corrosion begins to change into uniform corrosion.The corrosion product of the iron-zinc alloy should be a mixture of Zn O,Fe3O4,etc.With the extension of the corrosion time,the corrosion rate tends to remain stable and unchanged,about 0.26mm year^-1.