| Zinc,as an essential element for the human body,participates in the synthesis of various substances and plays a role in maintaining the normal operation of various systems in the human body.Since its chemical activity is between magnesium and iron,its degradation rate is more suitable for interventional diagnosis and treatment fields such as bone repair and stents.This article aims to establish a new degradable zinc alloy system for bone repair,and systematically explore the microstructure,mechanical properties,degradability,and biocompatibility of Zn-Fe-Mg alloy.Firstly,the as-cast Zn-1Fe-xMg(x=0.1?1.5wt.%)alloy was prepared,and the influence of magnesium(Mg)content on the as-cast microstructure,mechanical properties,and biodegradability was explored.Considering the comprehensive properties of the alloy,the composition of the alloy is optimized.The microstructure of the Zn-1Fe-xMg alloy is composed of Zn matrix,Zn+Mg2Zn11 eutectic structure,and FeZn13 phase.The addition of Mg improves the grain refinement and the mechanical properties while promoting micro-galvanic corrosion between different phases.The corrosion sequence of different phases is different.Specifically,the eutectics first corrodes and then spreads to the Zn matrix while the FeZn13 phase corrodes the slowest.Since cast Zn-1Fe-1Mg has excellent comprehensive mechanical properties and appropriate corrosion rate,it is suitable as a representative of this alloy series to be further processed for exploring the potential of alloy properties.Afterward,the Zn-1Fe-1Mg alloy was further extruded to improve the overall performance.Before extrusion,a thermal simulation test was performed on the Zn-1Fe-1Mg alloy to explore the influence of temperature and deformation rate on the structure of the alloy.The Arrhenius formula is employed to calculate the thermal deformation stress index n and the thermal deformation activation energy Q.The drawn hot working map combined with the change of alloy structure determined the extrusion process of the alloy.It has been verified that this alloy has good processing properties.Subsequently,the alloy was hot-extruded to analyze the changes in its microstructure,mechanical properties,and biodegradability.Undergoing dynamic recrystallization(DRX),the grain size was refined,and the alloy exhibits a basal texture parallel to the extrusion direction.Compared with cast alloys,extruded alloys have higher strength and elongation.The extruded alloy has three groups of corrosion micro-battery systems,with a higher electrochemical corrosion rate and lower impedance.In the immersion corrosion experiment,the corrosion layer on the surface of the extruded alloy fell off quickly,and the corrosion rate was about 0.067mm/a,which was faster than that of the as-cast alloy and far below the allowable limit of human zinc intake.The extruded alloy exhibits a more uniform corrosion morphology than cast alloy,and the corrosion pits are distributed in stripes parallel to the extrusion direction.Furthermore,the corrosion sequence and state of Mg2Zn11,Zn matrix,and FeZn13 were determined,and the corrosion model of alloy in SBF solution was established.Finally,the cytotoxicity,blood compatibility,and animal safety of the alloy are evaluated.Specifically,L929 and MC3T3-E1 cells presented good tolerance in the diluted extruded alloy leaching and even promoted cell proliferation.The alloy exhibited a low hemolysis rate and excellent anticoagulant ability,and the surface of the alloy would not cause platelet activation.Bone nail implantation experiments in SD rats demonstrated that the content of trace elements in serum was normal,with good animal compatibility.Besides,3D modeling was performed on the bone nail and its surroundings.The alloy bone nail was slowly degraded,and the formation of new bone and the healing of the defect was accelerated by the release of Zn and Mg ions.In this paper,the composition design and in-vitro properties of the degradable Zn-Fe-Mg alloys are preliminarily explored.It is revealed that this alloy has excellent mechanical properties and a suitable degradation rate,enabling it to meet the requirements of most bone repair biodegradable materials.Thus,certain preliminary preparations have been made for the development of the alloy-based biodegradable zinc alloy. |
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