Effect Of Nd And Y On Microstructures And Properties Of Zn-0.5Mg Alloy

Presently,the non-biodegradable medical metal materials used in clinical practice mainly include stainless steel,nickel-titanium alloy and cobalt-chromium alloy,etc.,which are permanently retained in the body as foreign bodies after implantation,causing different degrees of inflammatory reactions and requiring secondary surgical removal.Accordingly,the research needs of biodegradable medical metal materials are put forward and biodegradable medical metal materials represented by magnesium alloy and iron alloy are one of the research hotspots.However,the corrosion rate of magnesium alloy is too fast and that of ferroalloy is too slow,which restricts its clinical application.But,the mechanical properties of pure zinc are poor,and there is serious local corrosion in human physiological environment,which limits its wide application in clinical medicine.Therefore,the research and development of new biodegradable medical zinc alloy are urgent.In this paper,based on the Zn-0.5Mg alloy,the existing forms of Nd element and Y element in the alloy were studied,as well as the influence of the Nd element and Y element on the mechanical properties and corrosion properties of the alloy.In this experiment,five groups of Zn-0.5 Mg-x Nd（Y）with different Nd（Y）contents were fused as medical alloys,and characterized by microstructure,mechanical properties,immersion weight loss analysis and electrochemical analysis.It has been discovered that with the increase of Nd content,the grain size of the experimental alloy and the size of the Nd₃Zn₁₁ phase changed significantly.When the content of the Nd element was 0.05 wt.%,the grain size of the alloy was the smallest,and the Nd₃Zn₁₁ phase was evenly distributed.Therefore,the mechanical properties of Zn-0.5Mg-0.05 Nd alloy were optimum,and its tensile strength and yield strength reached 143.7 MPa and 122.5 MPa,respectively.Weight loss and electrochemical experiments were carried out in 37℃Hanks solution,and the corrosion properties of the alloy in the simulated human environment were studied.The results show that,with the increase of Nd content,the weight loss and corrosion rate of the experimental alloy decrease in the first and then increase.When Nd content is 0.1 wt.%,the corrosion loss and corrosion rate of the alloy are the minima.The electrochemical experiment also showed that the self-corrosion current of Zn-0.5Mg-0.1Nd alloy was the minimum（Icorr=0.95μA/cm²）,so Zn-0.5Mg-0.1Nd alloy was the most corrosion-resistant.Y element has a certain refinement effect on the grain.When Y content is 0.1 wt.%,the grain size is relatively small and the yield strength of the alloy is relatively high.When Y content increases to 0.2 wt.%,YZn₁₂ appears to be skewed and the mechanical properties of the alloy decrease.When Y content is 0.1 wt.%,the comprehensive mechanical properties of the alloy are better.At this time,the tensile strength of Zn-0.5mg-0.1Y alloy is 135.9 MPa,the yield strength is 119.9 MPa,and the elongation is 2.3%.Electrochemical analysis and in vitro immersion weight loss experiment showed that the self-etching current density was the lowest when Y content was 0.1 wt.%（Icorr=0.45μA/cm²）,and Zn-0.5 Mg-0.1 Y alloy had the best corrosion resistance.