生物用挤压态Mg-Zn-Y-Nd-xCu合金组织及性能的研究

发布时间：2018-03-01 00:07

  本文关键词： Mg-Zn-Y-Nd-xCu 合金 热 挤压 力学 性能 降解性能 抗菌性能　出处：《郑州大学》2017年硕士论文　论文类型：学位论文

【摘要】：生物镁合金具有良好的生物相容性、可降解性能及与人体密质骨相近的弹性模量,能够有效避免“应力遮挡效应”,具有非常广阔的应用前景。然而镁及其合金的力学性能和耐蚀性能比较差,不能满足医用金属材料的要求,且不具备抗菌作用,容易引发术后感染。本文在Mg-Zn-Y-Nd合金中添加具有抗菌作用的Cu元素,使合金具备抗菌性能,然后通过挤压加工处理,细化晶粒、改善合金的组织,从而提高合金的力学性能和耐蚀性能。采用OM、SEMEDS、XRD来分析合金的显微组织和物相组成;通过显微硬度、室温拉伸实验测试合金的力学性能;通过电化学实验、失重分析、析氢分析来测试腐蚀性能;最后通过体外抗菌实验分析合金的抗菌性能。铸态Mg-Zn-Y-Nd-xCu合金的晶粒粗大,组织不均匀,存在一定程度的枝晶偏析。随着Cu含量的增加,合金中第二相数量逐渐增多,并逐渐相互连接成网状结构。经过挤压加工后,合金的晶粒得到明显细化,组织变为等轴晶,第二相颗粒大部分固溶进基体,剩余部分弥散分布在晶粒内部。随着Cu含量的增加,挤压态Mg-Zn-Y-Nd-xCu合金的晶粒逐渐变小,晶粒尺寸由0.1wt.%Cu时的18μm减小到0.5wt.%Cu时的3μm。Cu加入以后合金中形成了CuMg2相,铸态Mg-Zn-Y-Nd-xCu合金的显微组织由镁基体和第二相(MgZn,CuMg2,Mg12YZn,Mg41Nd5)组成。经过挤压加工以后,只在挤压态Mg-Zn-Y-Nd-0.5Cu合金中检测到CuMg2二元相的存在,主要是因为含0.1wt.%Cu和0.3wt.%Cu的合金在热挤压过程中,Cu元素全部或者大部分固溶进入基体,导致含Cu第二相的体积分数大大减少,因此,没有检测出CuMg2相的存在。铸态Mg-Zn-Y-Nd-xCu合金中CuMg2相的存在降低了镁合金的力学性能。经过挤压加工,合金的抗拉强度和伸长率都得到明显的提高,其中挤压态Mg-Zn-Y-Nd-0.1Cu合金的抗拉强度能够达到325MPa。随着Cu含量的增加,挤压态合金的力学性能逐渐降低。由于Cu的加入,合金中形成了CuMg2相,在腐蚀过程中该相和镁基体形成原电池,增加了镁合金基体的电偶腐蚀,降低了镁合金的耐蚀性能。经过挤压加工以后,合金的晶粒得到明显细化,组织比较均匀,并且第二相颗粒大部分固溶进入基体中,挤压态合金的耐蚀性能优于铸态合金。随着Cu含量的增加,挤压态合金的耐蚀性能逐渐降低。通过抗菌实验可知,挤压态Mg-Zn-Y-Nd合金本身则不具有抗菌作用,挤压态Mg-Zn-Y-Nd-xCu合金对大肠杆菌和金黄色葡萄球菌的抗菌率均在99%以上,符合Ⅰ级抗菌材料的要求,具有强烈的抗菌作用。随着Cu含量的增加,挤压态合金的抗菌性能逐渐增加。通过对Mg-Zn-Y-Nd-xCu合金进行挤压加工,以期获得合金在有限的服役期内,能够保持机械性能的稳定性,同时在降解过程中释放的Cu离子又具有很好的抗菌效果,为镁合金作为医用材料的临床应用提供理论依据。
[Abstract]:Magnesium alloys have good biocompatibility, biodegradability and elastic modulus similar to those of human dense bone. It can effectively avoid the "stress shielding effect", and has a very broad application prospect. However, the mechanical properties and corrosion resistance of magnesium and its alloys are relatively poor, which can not meet the requirements of medical metal materials, and have no antimicrobial effect. It is easy to cause postoperative infection. In this paper, the antibacterial Cu element is added to the Mg-Zn-Y-Nd alloy to make the alloy have antibacterial properties, and then through extrusion processing, the grain size is refined and the microstructure of the alloy is improved. In order to improve the mechanical properties and corrosion resistance of the alloy, the microstructure and phase composition of the alloy were analyzed by OMSEMEDS XRD, the mechanical properties of the alloy were tested by microhardness and tensile test at room temperature, and the mechanical properties of the alloy were measured by electrochemical experiment and weightlessness analysis. The corrosion resistance was tested by hydrogen evolution analysis. Finally, the antibacterial properties of the as-cast Mg-Zn-Y-Nd-xCu alloy were analyzed by in vitro antibacterial experiments. The as-cast Mg-Zn-Y-Nd-xCu alloy had coarse grains, uneven microstructure and a certain degree of dendritic segregation. The number of the second phase in the alloy gradually increased, and gradually connected to each other into a network structure. After extrusion, the grain size of the alloy was obviously refined, the structure was changed into equiaxed crystal, and most of the second phase particles were dissolved into the matrix. With the increase of Cu content, the grain size of extruded Mg-Zn-Y-Nd-xCu alloy becomes smaller, and the grain size decreases from 18 渭 m at 0.1wt.Cu to 3 渭 m.Cu at 0.5wt.Cu to form CuMg2 phase. The microstructure of the as-cast Mg-Zn-Y-Nd-xCu alloy is composed of magnesium matrix and the second phase MgZnZn-CuMg2OMg-12YZnOMg-41Nd5. After extrusion processing, the existence of binary phase of CuMg2 is detected only in the extruded Mg-Zn-Y-Nd-0.5Cu alloy. It is mainly because the alloy containing 0.1wt.Cu and 0.3wt.Cu is completely or mostly dissolved into the matrix during hot extrusion, resulting in the decrease of the volume fraction of the second phase containing Cu. No CuMg2 phase was detected. The presence of CuMg2 phase in as-cast Mg-Zn-Y-Nd-xCu alloy reduced the mechanical properties of magnesium alloy. After extrusion, the tensile strength and elongation of the alloy were obviously improved. The tensile strength of the extruded Mg-Zn-Y-Nd-0.1Cu alloy can reach 325 MPA. With the increase of Cu content, the mechanical properties of the extruded Mg-Zn-Y-Nd-0.1Cu alloy decrease gradually. Due to the addition of Cu, the CuMg2 phase is formed in the alloy. The galvanic corrosion of magnesium alloy matrix is increased, and the corrosion resistance of magnesium alloy is reduced. After extrusion, the grain size of the alloy is refined and the microstructure is uniform, and most of the second phase particles are dissolved into the matrix. The corrosion resistance of the extruded alloy is better than that of the as-cast alloy. With the increase of Cu content, the corrosion resistance of the extruded alloy decreases gradually. The antibacterial rates of extruded Mg-Zn-Y-Nd-xCu alloy against Escherichia coli and Staphylococcus aureus were above 99%, which met the requirements of class I antibacterial materials and had strong antibacterial effect. The antibacterial properties of the extruded alloy gradually increased. By extruding the Mg-Zn-Y-Nd-xCu alloy, the stability of the mechanical properties of the alloy was obtained during the limited service period. At the same time, the release of Cu ions in the degradation process has a good antibacterial effect, which provides a theoretical basis for the clinical application of magnesium alloys as medical materials.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.22;R318.08

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