Microstructure,Mechanical Properties And Corrosion Resistanc Of Mg-Zn Alloy Wires For Medical Use

Biomedical magnesium alloy materials have good mechanical properties and biosafety,and can also be completely degraded in vivo,avoiding the risk of instrument retention in vivo and secondary surgical removal,which has broad application prospects in the field of biomedical instruments.However,the forming ability of magnesium alloy limits the development of high-performance magnesium alloy medical devices.There is a lack of understanding of the microstructure,mechanical properties and corrosion behavior of magnesium alloy prepared into instruments.Therefore,the processing technology and related properties of biomedical magnesium alloy instruments are of great significance.In this paper,Mg-Zn binary alloy was taken as the research object,and Mg-xZn(x=3,4,5,6 wt.%)alloy wires with diameter of 0.3 mm were prepared by multi-pass hot drawing process,and Biomedical anastomosis nails were prepared by using these wires.The effects of alloy composition and process on the microstructure,mechanical properties and corrosion properties of Mg-Zn alloy wires were systematically studied.At the same time,the effects of staples preparation process on the mechanical properties and corrosion properties of magnesium alloy materials were analyzed.The results of microstructure study show that complete dynamic recrystallization occurs in the formed Mg-Zn alloy wire,and the grain size decreases with the increase of Zn content.The increase in Zn content also resulted in the increase in the number of second phases.The two alloy wires,Mg-3Zn and Mg-4Zn,formed nearly single-phase microstructure.Uniformly distributed precipitates appeared in the Mg-5Zn alloy wire,while a large number of precipitates distributed along the deformation direction appear in the Mg-6Zn alloy wire,and these precipitates and matrix grains constitute an obvious banded structure.The results of mechanical properties showed that the strength and elongation of the wire increased with the increase of Zn content from 3 wt.%to 5 wt.%.The maximum tensile strength and elongation of Mg-5Zn alloy wire reached 350 MPa and 260 MPa,respectively,and the elongation reached 16.5%.When the Zn content was 6 wt.%,the strength and elongation of the wire decreased.The results of electrochemical experiments show that the self-corrosion potential of Mg-Zn alloy wires increases with the increase of Zn content.When the Zn content increased from 3 wt.%to 5 wt.%,the self-corrosion current density of the wire decreased,while when the Zn content was 6 wt.%,the self-corrosion current density of the wire increased.The immersion test results show that the corrosion rate of Mg-3Zn and Mg-6Zn alloy wires is faster than that of Mg-4Zn and Mg-5Zn alloy wiresIn this paper,Mg-4Zn and Mg-5Zn alloy wires were prepared into anastomotic nails,and the wire was processed by cold deformation of simulated instrument molding.Cold deformation causes deformation twins in the microstructure and leads to obvious work hardening.Electrochemical analysis showed that the self-corrosion potential of the wire did not change significantly after cold deformation,but the corrosion current density increased slightly.The overall corrosion of the anastomosis nail was uniform,but the local position where large bending deformation occurred was more serious than that of other parts without bending deformation.The results show that magnesium alloy wire and equipment with good mechanical properties and corrosion resistance can be prepared by multi-pass hot drawing process and controlling zinc content in magnesium zinc alloy,which can provide support for the development of high-performance biodegradable equipment technology.