【作者】 郭亮；

【导师】 曹占义；

【作者基本信息】 吉林大学 ， 材料学， 2014， 硕士

【摘要】 镁锌钙合金由于具有较高的比强度和比刚度，且弹性模量与人体骨骼相近，同时具有良好的生物相容性，是目前医用合金领域的研究热点，但该系列合金的力学性能和耐蚀性还没有达到应用的标准，而据研究合金元素Zr和Nd可以显著改善镁合金的显微组织，提高镁合金的力学性能和耐蚀性。本工作制备了铸态和固溶态Mg-4Zn-0.5Ca-xZr（x=0.2，05，0.8）和Mg-4Zn-0.5Ca-xNd（x=1，2，3）合金，并分别进行了测试分析。通过金相、SEM、EDS和XRD实验，分析了合金元素和固溶处理对显微组织的影响；通过拉伸测试和断口观察，分析了显微组织改变对合金力学性能的影响；通过析氢实验、电化学测试和腐蚀形貌观察，分析了显微组织改变对合金耐蚀性的影响。得出如下主要结论：1）铸态Mg-4Zn-0.5Ca-xZr合金的显微组织由α-Mg、Ca2Mg6Zn3相和Zr单质相组成。随Zr含量的增加，晶粒不断细化，固溶处理后晶粒内部和晶界处大量Ca2Mg6Zn3相溶入基体中，在晶粒内部还出现了少量的椭圆形Mg2Zn3相；随Zr含量的增加，铸态Mg-4Zn-0.5Ca-xZr合金的力学性能不断提高，Zr含量为0.8wt.%时，屈服强度达到最大值126MPa，Zr含量为0.5wt.%时，抗拉强度和延伸率分别达到最大值197MPa和16%，固溶处理后各项力学性能指标进一步提高，当Zr含量为0.5wt.%时，屈服强度和抗拉强度分别达到最大值146MPa和243MPa，当Zr含量为0.2wt.%时，延伸率达到最大值18.1%；随Zr含量的增加，铸态Mg-4Zn-0.5Ca-xZr合金的耐蚀性也显著提高，当Zr含量达到0.5wt.%时，具有最佳耐蚀性能，析氢速率和腐蚀电流密度分别达到最小值0.0177ml/cm2·h和6.18μA·cm-2，腐蚀电位达到最大值-1.51V，固溶处理后，耐蚀性进一步提高，当Zr含量为0.5wt.%时，析氢速率和腐蚀电流密度分别达到最小值0.0166ml/cm2·h和5.164μA·cm-2，腐蚀电位增大到最大值-1.492V。2）铸态Mg-4Zn-0.5Ca-xNd合金的显微组织由α-Mg、Ca2Mg6Zn3相、Mg2Zn3相和Mg12Nd相组成，随Nd含量的增加，晶粒不断细化，出现很多细小的枝晶，整体形态由枝晶向等轴晶转变，固溶处理后晶粒内部和晶界上部分Ca2Mg6Zn3相和Mg2Zn3相溶入基体，晶界变的不连续，枝晶消失；随Nd含量的提高，铸态Mg-4Zn-0.5Ca-xNd合金的力学性能不断提高，当Nd含量达到2wt.%时，屈服强度、抗拉强度和延伸率分别达到最大值110MPa、192MPa和14.4%，固溶处理后力学性能进一步提高，当Nd含量达到2wt.%时，屈服强度、抗拉强度和延伸率分别达到最大值135MPa、227MPa和16.9%；随Nd含量的提高，铸态Mg-4Zn-0.5Ca-xNd合金的耐蚀性也显著提高，当Nd含量达到2wt.%时，析氢速率和腐蚀电流密度分别达到最小值0.0261ml/cm2·h和12.22μA·cm-2，腐蚀电位达到最大值-1.462V，具有最佳耐蚀性能，固溶处理后，耐蚀性进一步提高，当Nd含量达到2wt.%时，析氢速率和腐蚀电流密度分别达到最小值0.0155ml/cm2·h和10.42μA·cm-2，腐蚀电位增大到最大值-1.338V。更多还原

【Abstract】 As Mg-Zn-Ca alloy has high strength and stiffness, it’s elastic modulus is similar to thatof human bone’s and it also has good biocompatibility, becoming a hot research field ofmedical alloys nowdays. However, the mechanical properties and corrosion resistance of thisseries alloy has not yet reached the standard of application, according to related research,theaddition of Zr and Nd into magnesium alloys can significantly improve the microstructure,and improve the mechanical properties and corrosion resistance performance at the sametime.In this article, cast and soluted treated Mg-4Zn-0.5Ca-xZr and Mg-4Zn-0.5Ca-xNdalloys have been prepared, tested and analysised. Analysed the impact of alloying elementsand solution treatment on microstructure through metallographic, SEM, EDS and XRDexperiment; Analysed the impact of changes of microstructure on the mechanical propertiesthrough tensile testing and observed fracture morphology; Analysed the effect of changes ofmicrostructure on corrosion resistance performance through observing corrosion morphology,hydrogen collection experiments and electrochemical test. The main conclusions are asfollows:1) The mirostructure of as-cast Mg-4Zn-0.5Ca-xZr alloy are composed of α-Mg,Ca2Mg6Zn3phase and Zr elemental phase, with the increasing the content of Zr, grain areconstantly refined, large amount of Ca2Mg6Zn3phase from the internal and boundary ofgrain have integrated into matrix after solution treatment,small amount of Mg2Zn3phasealso appeared in the interal grains; With the increasing of the content of Zr, the mechanicalproperties of as-cast Mg-4Zn-0.5Ca-xZr alloy are continuously improved, when the contentof Zr reached0.8wt.%, yield strength reaches the maximum of126MPa, when the content ofZr reached0.5wt.%, the tensile strength and elongation rate reaches the maximum of197MPa and16%respectively,after the mechanical properties of this alloy get furtherimprovement after solution treated,when the content of Zr reached0.5wt.%,the yieldstrength and tensile strength reached the maximum of146MPa and243MPa respectively,when the content of Zr reached0.2wt.%,the longation reached the maximum of18.1%;With the increasing of the content of Zr,the corrosion resistance performance of as-castMg-4Zn-0.5Ca-xZr alloy is significantly increased,when the content of Zr reached0.5wt.%,the hydrogen evolution rate and corrosion current density reaches the minimum of0.0177 ml/cm2·h and6.18μA·cm-2respectively, the corrosion potential reaches the maximum of-1.51V, this kind of alloy has the best corrosion resistance performance,the corrosionresistance of this alloy get further improvement after solution treated, when the content of Zrreached0.5wt.%, the hydrogen evolution rate and corrosion current density reaches theminimum of0.0166ml/cm2·h and5.164μA·cm-2respectively, the corrosion potential reachesthe maximum of-1.492V.2) The microstructure as-cast Mg-4Zn-0.5Ca-xNd alloy are composed of α-Mg,Ca2Mg6Zn3phase, Mg2Zn3phase and Mg12Nd phase, with the increasing the content of Nd,rain are constantly refined, many small dendrites appered, overall microstucture changefrom dendritic to equiaxed crystal,part of Ca2Mg6Zn3phase and Mg2Zn3phase from grainboundary integrated into matrix after solution treatment,the grain boundary becomesdiscontinuous,and dendrite disappeared;With the increasing of the content of Nd, themechanical properties of as-cast Mg-4Zn-0.5Ca-xNd alloy are continuously improved, whenthe content of Nd reached2wt.%, yield strength, tensile strength and elongation rate reachesthe maximum of110MPa,192MPa and14.4%respectively, the mechanical properties ofthis alloy get further improvement after solution treated, when the content of Nd reached2wt.%, the yield strength, tensile strength and elongation rate reaches the maximum of135MPa、227MPa and16.9%;With the increasing of the content of Nd,the corrosionresistance performance of as-cast Mg-4Zn-0.5Ca-xNd alloy is significantly increased,whenthe content of Zr reached2wt.%, the hydrogen evolution rate and corrosion current densityreaches the minimum of0.0261ml/cm2·h and12.22μA·cm-2respectively, the corrosionpotential reaches the maximum of-1.462V, this kind of alloy has the best corrosionresistance performance,the corrosion resistance of this alloy get further improvement aftersolution treated, when the content of Nd reached2wt.%, the hydrogen evolution rate andcorrosion current density reaches the minimum of0.0155ml/cm2·h and10.42μA·cm-2respectively, the corrosion potential reaches the maximum of-1.338V.更多还原