心血管支架用可降解Mg-Y-Zn-Zr合金组织及性能研究

发布时间：2018-06-03 17:47

本文选题：Mg-Y-Zn-Zr合金 + 显微组织　；参考：《太原理工大学》2017年硕士论文

【摘要】：冠心病是危害人类健康的重大疾病之一,在动脉血管中植入支架是治疗冠心病的常用方法。镁合金具有良好的生物相容性和自发降解性,使其成为血管支架的理想材料。但是镁合金也存在着强度较低、耐腐蚀性能较差等缺点,制约了其在临床上的应用。本文旨在开发性能优异的新型可降解镁合金血管支架材料。本实验选用生物安全性良好的Zn、Y、Zr元素作为合金化元素,通过常规铸造法制备了Mg-xY-3Zn-0.4Zr(x=0,1,2,3,4 wt.%)合金和Mg-2Y-yZn-0.4Zr(y=0,1,2,4,5 wt.%)合金,并对优选出的最佳成分合金进行热处理。采用OM、SEMEDS、XRD、失重法、析氢法、电化学测试和室温拉伸等方法,对比研究了Y、Zn元素及热处理工艺对合金显微组织、力学性能和耐腐蚀性能的影响。实验结果表明:添加Y元素能够显著细化合金晶粒。Mg-3Zn-0.4Zr合金主要由α-Mg和小颗粒状Mg0.97Zn0.03相组成;当Y含量为1 wt.%时合金中出现长条状Mg3YZn6相(I相);当Y含量为2 wt.%时合金中出现鱼骨状Mg3Y2Zn3相(W相)。少量Y的加入,促进I相的形成,I相与Mg基体电位差较小,形成的微电池数量减少。此外,Y元素与合金中的Fe、Mn等杂质元素形成金属间化合物,提纯熔液,改善合金的耐腐蚀性能。过量Y的加入形成硬脆的W相呈网状分布在晶界上,W相与镁基体结合键较弱,易产生微裂纹。且第二相数量较多时,合金产生严重的偏析现象,降低合金的力学性能。Mg-2Y-3Zn-0.4Zr合金表现出最佳的综合性能。与Y元素相比,添加Zn元素对合金的晶粒细化作用有限。Mg-2Y-0.4Zr合金主要由α-Mg基体和Mg24Y5相组成;Mg-2Y-1Zn-0.4Zr合金由α-Mg基体和I相组成;继续增加Zn含量,合金中出现W相。微量的Zn元素能提高基体腐蚀电位,提高合金耐腐蚀性能。Zn溶入Mg基体中,产生固溶强化。过量的Zn产生大量的第二相,增加了合金电偶腐蚀的倾向。硬脆的W相聚集甚至割裂基体,降低合金力学性能。因此,随着Zn含量的增加,合金的耐腐蚀性能和力学性能均呈现出先增加后降低的趋势。Mg-2Y-1Zn-0.4Zr合金表现出最佳的综合性能。在热处理过程中,Mg-2Y-1Zn-0.4Zr合金的晶粒发生了一定程度的长大现象;热处理未改变合金的相组成(α-Mg基体和I相),长条状I相转变为颗粒状,均匀分布在基体上。T4-10态合金中大部分I相溶解,减少了合金中的微电池数量,耐腐蚀性能增强。T4-30态合金由于保温时间太长,晶粒严重粗化,总晶界面积减小,晶界对位错的阻碍作用减弱,且晶界上难熔的杂质密度增大,性能降低。时效处理后,基体上析出细小弥散分布的I相,起到弥散强化的作用。此外,析出相均匀分布在基体上,降低了局部腐蚀的倾向,耐腐蚀性能增强。本研究中,T6态综合性能最佳:失重平均腐蚀速率为0.189 mm/a,抗拉强度为258 MPa,屈服强度为144 MPa,伸长率为15.5%。该结果基本满足支架材料对力学性能和耐腐蚀性能的要求。
[Abstract]:Coronary artery disease (CHD) is one of the major diseases that endanger human health. Stent implantation in arterial vessels is a commonly used method in the treatment of coronary artery disease (CHD). Magnesium alloy has good biocompatibility and spontaneous degradation, which makes it an ideal material for vascular stent. However, magnesium alloys also have some disadvantages, such as low strength and poor corrosion resistance, which restrict their clinical application. The aim of this paper is to develop new degradable magnesium alloy vascular scaffolds with excellent performance. In this experiment, the Zn-ZY Zr alloy, which has good biological safety, was used as alloying element. Mg-xY-3Zn-0.4ZrxOZn-0.4ZrxCX 4wt.) alloy and Mg-2Y-YZn-0.4ZryZn-0.4ZryZn-0.4ZryZn-0.4ZryZn-0.4ZryZn-45wt.) alloy were prepared by conventional casting method, and the best component alloys were heat-treated. By means of OMSEMEDS XRD, weightlessness, hydrogen evolution, electrochemical measurement and room temperature tensile test, the effects of Y _ (Zn) and heat treatment on the microstructure, mechanical properties and corrosion resistance of the alloy were studied. The experimental results show that the addition of Y element can significantly refine the grain size of the alloy. Mg-3Zn-0.4Zr alloy mainly consists of 伪 -Mg and small granular Mg0.97Zn0.03 phase. When Y content is 1 wt.%, long stripe Mg3YZn6 phase I phase is found in the alloy, and fishbone Mg3Y2Zn3 phase W phase is found in the alloy when Y content is 2 wt.%. The addition of a small amount of Y promoted the formation of phase I and the potential difference between phase I and mg matrix was smaller, and the number of formed microbatteries decreased. In addition, Y element forms intermetallic compound with impurity elements such as Feo mn in the alloy to purify the melt and improve the corrosion resistance of the alloy. The hard and brittle W phase was formed by the addition of excess Y, and the bonding bond between W phase and magnesium matrix was weak on the grain boundary, resulting in microcracks easily. When the number of the second phase is higher, serious segregation occurs, and the mechanical properties of the alloy. Mg-2Y-3Zn-0.4Zr alloy shows the best comprehensive properties. Compared with Y element, the effect of Zn addition on grain refinement is limited. Mg-2Y-0.4Zr alloy is mainly composed of 伪 -Mg matrix and Mg24Y5 phase, which consists of 伪 -Mg matrix and I phase, and W phase appears in the alloy with increasing Zn content. Trace Zn element can increase the corrosion potential of the matrix and improve the corrosion resistance of the alloy. Zn is dissolved into the mg matrix, resulting in solid solution strengthening. Excessive Zn produces a large number of secondary phases, which increases the tendency of galvanic corrosion of the alloy. The hard and brittle W phase aggregates and even cleans the matrix, which reduces the mechanical properties of the alloy. Therefore, with the increase of Zn content, the corrosion resistance and mechanical properties of the alloy increased first and then decreased. Mg-2Y-1Zn-0.4Zr alloy showed the best comprehensive properties. The grain size of Mg-2Y-1Zn-0.4Zr alloy grew to a certain extent during heat treatment, and the phase composition (伪 -Mg matrix and I phase) was not changed after heat treatment. The dissolution of most of phase I in the matrix. T4-10 alloy reduces the number of microbatteries in the alloy. The corrosion resistance of the alloy is enhanced. Due to the long holding time, the grain size is coarsened and the total grain boundary area is decreased. The hindrance of the grain boundary to the dislocation is weakened, and the impurity density on the grain boundary increases and the performance decreases. After aging treatment, I phase was precipitated from the matrix, which played the role of dispersion strengthening. In addition, the precipitation phase is uniformly distributed on the matrix, which reduces the tendency of local corrosion and enhances the corrosion resistance. In this study, the comprehensive performance of T6 state is the best: the average weight loss corrosion rate is 0.189 mm / a, the tensile strength is 258MPa, the yield strength is 144MPa, and the elongation is 15.5 mm / a. The results basically meet the requirements of mechanical properties and corrosion resistance of scaffolds.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.22;R318.08

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