| Magnesium and its alloy have been widely applied in biomedical fields,owing to their surprisingly performances such as biocompatibility,biodegradability and the similar elastic modulus with human bone.Usually,it can be processed into wires to be used as cardiovascular weaving scaffold,surgical suture line,and bone repair material,so that people can avoid suffering from reoperation.However,the lattice structure of Mg and Mg alloys is hcp,which has poor plastic deformation ability at room temperature,therefore,people still face many challenges in the plastic processing of magnesium and its alloy.This article relies on the project of industrial science and technology breakthrough in Shaanxi Province and the project of science and technology plan in Weiyang district of Xian.In this paper,the problem about plastic processing of pure magnesium wire has been studied which can lay the foundation for its application in the field of biomedical.In this paper,the thermal compression experiments of pure Mg samples were carried out under condition with different strain rate and temperature respectively.Constitutive model was built according to the results of the thermal compression experiments.Using the established constitutive model,the drawing process of pure magnesium wire was numerically simulated to control the different friction coefficient,drawing speed and the amount of pass deformation,and then the process parameters was verified by experiments.The most suitable drawing parameters can be obtained through the surface observation,mechanical properties testing and microstructure analysis.In order to explore the best heat treatment,the Mg wire was annealed and then the microstructure of Mg wire after annealing was analyzed.The corrosion behavior of Mg wire with different cumulative deformation quantity in simulated body fluid was analyzed,and the influence of grain size on the corrosion resistance of Mg wire was discussed.The main conclusions are as follow:(1)According to the results of hot compression experiment,the establishment of pure magnesium constitutive equation was established:(?)(2)Under the condition of the selected simulation parameters,strain and stress and nonuniformity of the pulling force increase with the increase of the friction coefficient.With the increase of drawing speed,the pulling force does not change,the strain nonuniformity reached the largest,and the maximum main stress gradually increases.The maximum main stress increases dramatically at the drawing speed exceeding60 mm/s.With the increase of pass deformation,the fracture tendency value increases.It sharply increases at the level of pass deformation exceeding 15%.(3)When the lubricant with low friction coefficient,drawing speed less than 60mm/s,10%-15%pass deformation and about 40%cumulative deformation quantity were selected as the drawing process parameters of pure magnesium wire,,the obtained pure magnesium wire has better mechanical properties and uniform microstructure.What’s more,the Mg wire can meet the requirements of production efficiency.(4)The exploration of annealing process of demonstrates that the microstructure is uniform and the grain does not grow when the annealing temperature is 250℃ and the holding time is 30min.When the pure Mg wire was annealed at 250℃ for 30 min,fine and uniform grains formed and didn’t grow up further more.(5)The corrosion experiments of Mg wire with different grain sizes in simulated body fluid showed that the weight loss rate and average corrosion rate of the sample were smaller when the grain size was small..Furthermore,the corrosion resistance was better and the corrosion mode was uniform corrosion. |
