| In the recent years, the incidence rate of coronary heart disease has been rising year by year. The coronary heart disease has been one of the most dangerous diseases that can threaten our health and life safety. Percutaneous stent implantation can recover the blood flowing immediately after expansion and has immediate healing results. At present the stent implanted will stay in our body forever unless taken out by the second surgery. The stent in our body can induce chronic inflammation and restenosis which has bad effect on the treatment. Biodegradable stent can disappear from our body after curing the sicken vessel. It has much better treatment than the traditional metallic stent. The most important of studying biodegradable stent is finding a biomaterial suitable for biodegradable implanting. People have paid much more attention on Iron in the biodegradable implanting field. A lot of studies have revealed that pure Iron has super biocompatibility and mechanical property, but its degradation rate is too slow to satisfy the requirement of biodegradable stent. The pure Iron would be widely used in the biodegradable implanting field, if only its degradation rate can be increased.Zinc has lower electrode potential and preferable biocompatibility. In this paper we want to adjust the degradation rate of Fe-Zn alloy by design a series of Fe-Zn alloys. Since Iron and Zinc have no mutual solid solubility at room temperature, we can not get homogeneous Fe-Zn alloy by the traditional melting. Firstly, the Fe-Zn alloy powders were prepared by Mechanical Alloying, then we prepared the Fe-Zn alloy solid by Spark Plasma Sintering. A series of Fe-Zn alloys that the mass fraction of Zinc were5%,10%,15%,20%,25%and30%were prepared respectively by10h ball-milling. The phase transition law of Fe-Zn alloys with different composition was investigated. The Fe-Zn alloys that the mass fraction of Zinc was15%were prepared by20h,30h,40h and50h ball-milling, respectively. The effect of ball-milling time on the properties of Fe-Zn alloy was studied. The ball-milling powders were sintered by Spark Plasma Sintering, the sintering experiment parameters were sintering temperature800℃, holding time1min and sintering pressure50MPa. The microstructure and composition of the Fe-Zn alloys were studied. We also investigated the degradation behavior deeply in this paper.The results showed that the powders after ball-milling were fine and homogeneous. The powders become finer and the component Zinc has better solution in the matrix Iron when we prolonged the ball-milling time. The Fe-Zn alloys were found to be composed of Fe-Zn solid solution matrix and fine ZnO particles. The results of potentiodynamic polarization showed that the Fe-Zn alloys have lower electrode potential than pure Iron in SBF simulated body fluid. But when the mass fraction of Zinc increased, the amount of ZnO particles increased too. It made the electrode potential of Fe-Zn alloys approach the pure Iron. The static immersion experiment of the Fe-Zn alloys that the mass fraction of Zinc was15%of20h,30h,40h and50h ball-milling showed that there were corrosion pits formed after14days immersion in SBF simulated body fluid. There was compound composed of Calcium and Phosphorus formed on the surface of the sample of50h ball-milling. All of the degradation rates calculated by weight loss were higher than pure Iron, especially the sample of50h ball-milling whose degradation rate was almost two times of pure Iron. Since the Fe-Zn alloy prepared by powder metallurgy has better degradation property than pure Iron, it should be investigated much more deeply as a new biodegradable metal. |
PDF Full Text Request