As a new generation of human implant materials,biological magnesium alloys have attracted the attention of global researchers in recent years.The study found that when magnesium alloys implanted in the body,magnesium alloys will natural degradation,so as to avoid the secondary damage to human body and operation cost,and the natural degradation of magnesium ion is non-toxic side effects,and irritating,also no rejection and bad phenomenon in the human body.Instead will also participate in human metabolism,excess magnesium ions could be ruled out in vitro..Compared with the widely used titanium alloy,316 L stainless steel,cobalt chromium alloy and so on,Biological magnesium alloy has the advantages of biological safety,biodegradability and the closest density and elastic modulus,However,the corrosion and mechanical properties of magnesium alloys are not high,which has been the key problem to hinder its wide application.The research work of this paper is mainly based on alloying,Add Sr,Zr,Sn,Ca and other elements,Then the alloy rolling,extrusion,heat treatment process,To improve the mechanical properties and corrosion resistance of magnesium alloy,The main conclusions are as follows:1、The rolling magnesium alloy mainly consists of α-Mg as matrix,rich Zr region and Mg17Sr2,CaMgSn and so on.Zr,Sr,Ca,Sn and other elements can refine the microstructure to improve corrosion resistance and mechanical properties,But the study found,According to Mg-Zr two phase diagram,The maximum solid solubility of Zr in liquid magnesium in 0.8%,Although due to the addition of element Ca on the solubility of Zr increased the positive significance but the combination of the results of the experiment,Zr should not be greater than 1%,Similarly,the content of Sr increased and then decreased,According to the microstructure and properties of 5groups of magnesium alloys,it is more appropriate to control the amount of alloying element Sr in 1.5-3 wt.%.2、The corrosion resistance is determined by the grain size and the content and distribution of the second phase.The grain size of alloy 5(Mg-1.5Sr-0.5Sn-0.5Ca)is not the smallest,and the corrosion resistance is the best.The tensile strength of alloy5 alloy is 180 Mpa,The compressive strength can reach 340 Mpa,and the hydrogen evolution corrosion rate is 0.68 ml/(cm2day).Therefore,it is significant to study the distribution law and mechanism of the second phase in the magnesium alloy.3、The microstructure of the extrusion process is similar to that of the rollingprocess,and the microstructure becomes more uniform after Homogenizing annealing.When the insulation temperature is determined,the holding time is one of the important factors that affect the organization,after the extrusion of Mg-x Sr-yZr-z Sn-0.5Ca homogenizing annealing,when the temperature is 450℃,the heat preservation time should not exceed 12 hours.4、The corrosion of magnesium alloys with local corrosion(especially pitting corrosion)and grain boundary corrosion,alloy1 SEM can be seen in the vicinity of the grain boundaries of Zr rich,have eroded the left hole,by Tafel curve fitting that the corrosion rate of alloy1 alloy was 3.29(mm/year),alloy1 alloy after homogenizing annealing treatment on compressive strength after the increased 68%,reaching 510 Mpa. |