Fine Thin-walled Magnesium Alloy Tube Plastic Forming Technology And Biological Compatibility

At present,with serious threats of cardiovascular disease to human health,stent implantation has become wider,but many stent are made of stainless steel,nickel titanium alloy and other non-degradable stent.Because non-degradable stent would damage human body again,magnesium alloy,as a new type of biodegradable materials,has aroused people's attention.With good mechanical properties and low toxicity,the rare earth magnesium alloy has unparalleled advantages in the same type programs.This paper focuses on rare earth magnesium alloy.By putting different amount of rare earth Nd in Mg-Y-Zr alloy,it aims to explore how Nd influences mechanical properties of Mg alloy,microstructure,corrosion resistance as well as cell toxicity,and to obtain a magnesium alloy substrate mechanical properties and biocompatibility of better stent.Making fine thin vascular stent by hot extrusion and drawing,it explores the reasonable heat treatment pipe system.By putting different amount of rare earth Nd from 0% to 6% in Mg-4Y-0.5Zr alloy,The tensile strength of Mg-4Y-xNd-0.5Zr alloy increases first and then decreases.When the Nd amount is 3%,the maximum tensile strength of alloy reaches to 193 MPa,and tensile strength of Mg-4Y-xNd-0.5Zr has been reduced with the decrease of Nd.When the Nd is 0%,the elongation of the alloy reaches 9%.The static immersion test of Mg-4Y-x Nd-0.5Zr alloy showed that the average corrosion rate of the alloy decreases first and then increased along the increase of Nd amount.When the Nd content is 3%,the average corrosion rate of the alloy is the lowest,0.039mg/cm2 h.When the Nd content is 4.5%,the average corrosion rate of the alloy is up to 6.63mg/cm2h;after observing the degree of corrosion,The alloy is the partial corrosion without Nd,and with the increase of Nd content,the alloy is uniform corrosion.When the Nd content reaches 6%,the alloy corrosion is the most serious.Found in vitro experiments on AM50,Mg-4Y-4.5Nd-0.5Zr,Mg-4Y-6Nd-0.5Zr,Mg-4Y-3Nd-0.5Zr,cytotoxicity extract of this four alloys was low,and there was no effect on the activity of human umbilical vein endothelial cells.In the process of 24 h extraction,Mg-4Y-4.5Nd-0.5Zr alloy degraded fast with many pits on the surface and more the dissolution of ions.Mg-4Y-3Nd-0.5Zr alloy has less ion dissolution and better corrosion resistance.The results showed that the surfaces of Mg-4Y-4.5Nd-0.5Zr and Mg-4Y-6Nd-0.5Zr alloy were formed by more dendritic corrosion products which were attached to the surface of the cell and affected the cells activity.The corrosion products of AM50 and Mg-4Y-3Nd-0.5Zr alloys are less,but the surface cells growth of Mg-4Y-3Nd-0.5Zr alloy is better than that of other alloys.Hot extrusion Mg-4Y-3Nd-0.5Zr alloy can get the good surface quality of extruded pipe by use reasonable parameters.After dealing with the pipe T5 and T6,the tensile strength of pipe was up to 286 MPa at 225?x14h;When the pipes are under the condition of 525?x 8h+225?x14h,the comprehensive performance of the pipe is good,and the tensile strength of the pipe reaches 269 MPa,the elongation 13.8%;With drawing of tube extrusion 10 times,speed is 0.2mm/s,the annealing temperature is 400?,heat preservation for 10 min,could pull out tube with diameter 4mm and wall thickness of 0.25 mm,The pipe wall thickness.