心血管支架用生物可降解Mg-Zn-Gd-Zr镁合金的组织及性能研究

发布时间：2018-04-09 03:24

  本文选题：Mg-Zn-Zr-Gd合金　切入点：Gd元素　出处：《太原理工大学》2017年硕士论文

【摘要】：镁元素是人体必需的一种营养元素,并且镁合金在人体的环境中有良好的生物相容性,又由于它在人体内形成的腐蚀产物无毒无害,所以镁合金常常被作为生物材料应用在医学中,例如镁合金作为血管支架的常用材料,在当植入人体后的支架材料,在人体的环境中经过缓慢的降解,最终被新生成的骨组织取代,这样就避免了从患者体内取出植入件而带来的二次手术的痛苦,同时还大大减少了医疗费用。但是,因为镁合金在液体环境中腐蚀速度快,这样就有可能导致导致了患者未完全治愈之前,植入的支架材料就丧失了完整的力学性能,这一缺点则在很大程度上限制了镁合金作为植入材料在医学上的广泛应用。本课题选取了生物相容性良好的Gd、Zn和Zr作为合金材料,研究Gd对Mg-Zn-Zr合金的力学性能及腐蚀性能的影响,并确定最优的合金成分,在此基础上继续研究了挤压温度对合金的性能影响,并最终确定最佳的挤压温度。具体研究结果如下:(1)铸态合金中,不同Gd含量(0wt.%、1wt.%、2wt.%、3wt.%)的Mg-4Zn-x Gd-0.4Zr合金,随着Gd含量的增加,合金的晶粒尺寸有明显减小的趋势。Gd含量越多,晶粒组织越细小,力学性能也就越好,Mg-4Zn-0.4Zr-3Gd表现出了最佳的力学性能。同时Gd元素的变化,影响了合金中相的组成,Mg-4Zn-0.4Zr合金由镁基体和Mg0.97Zn0.03二元相组成,当添加Gd元素之后Mg-4Zn-0.4Zr-1Gd、Mg-4Zn-0.4Zr-2Gd以及Mg-4Zn-0.4Zr-3Gd主要由镁基体、Mg0.97Zn0.03相和Mg3Gd相组成,并且Mg3Gd相的体积分数随着Gd含量的增加而增加。(2)铸态合金中晶粒的细化能够增强耐腐蚀性能,同时存在适量的Mg3Gd也会增强耐蚀性能,但是Mg3Gd的含量超过一定的值时会削弱镁合金的耐腐蚀性能,Mg-4Zn-0.4Zr-1Gd合金具有比较细化的晶粒尺寸和存在少量的Mg3Gd相,综合作用下表现出了最佳的性能。(3)挤压工艺可以有效的细化晶粒;材料的挤压温度较低可以有效的抑制晶粒的长大,250℃时合金的晶粒尺寸最小;挤压之后合金组织并不完全均匀化。(4)挤压温度为250℃时,第二相破碎比较明显,颗粒状形态的第二相较多,颗粒也较小;当随着温度升高到350℃时,第二相的破碎程度逐渐减小,并且第二相体积分数也随着降低。与铸态相比,挤压温度的变化并没有改变合金的相的组成,合金仍然是由α-Mg、Mg0.97Zn0.03以及少量的Mg3Gd相组成。(5)挤压态合金在浸泡初期,腐蚀速率会突然增大,然后慢慢的变得平缓稳定,随着温度的升高,合金的腐蚀速率越低,耐腐蚀性能也会越好。当挤压温度为350℃,合金的抗腐蚀性能最佳。平均腐蚀速率为0.42mm/a。(6)电化学腐蚀试验中,挤压温度为250℃时,自腐蚀电位是-1.62V,挤压温度升高到300℃,自腐蚀电位也随着升高到-1.54V,当温度继续升高到350℃,自腐蚀电位升高到-1.52V。随着挤压温度的升高,合金的自腐蚀电位就会变得越正。在温度为350℃时具有最佳的耐腐蚀性能,与失重实验的结果一致。
[Abstract]:Magnesium is a necessary nutrient element in human body, and magnesium alloy has good biocompatibility in human environment, and the corrosion products formed in human body are non-toxic and harmless.So magnesium alloys are often used as biomaterials in medicine, such as magnesium alloys as common materials for vascular stents, and the scaffolds that are implanted in humans are slowly degraded in the human environment.It was eventually replaced by new bone tissue, thus avoiding the pain of secondary surgery to remove implants from patients and greatly reducing medical costs.However, because magnesium alloys corrode rapidly in liquid environments, this may lead to the loss of complete mechanical properties of the scaffold materials before the patient is fully cured.This disadvantage limits the wide application of magnesium alloys as implants in medicine to a large extent.The effect of Gd on the mechanical and corrosion properties of Mg-Zn-Zr alloy was studied, and the optimum alloy composition was determined.On this basis, the influence of extrusion temperature on the properties of the alloy was studied, and the optimum extrusion temperature was determined.The specific results are as follows: (1) in the as-cast alloy, the grain size of the Mg-4Zn-x Gd-0.4Zr alloy with different Gd contents and different Gd contents is 0 wt.and 2wt.and 3wt.k.) with the increase of Gd content, the grain size of the alloy tends to decrease obviously. The more Gd content, the smaller the grain structure.The better the mechanical properties are, the better the mechanical properties of Mg-4Zn-0.4Zr-3Gd are.The composition of Mg-4Zn-0.4Zr alloy is composed of magnesium matrix and Mg0.97Zn0.03 binary phase. After the addition of Gd element, Mg-4Zn-0.4Zr-0.4Zr-2Gd and Mg-4Zn-0.4Zr-2Gd are mainly composed of mg _ (0.97) Zn _ (0.03) and Mg3Gd phases.And the volume fraction of Mg3Gd phase increases with the increase of Gd content.However, when the content of Mg3Gd exceeds a certain value, the corrosion resistance of magnesium alloy will be weakened. Mg-4Zn-0.4Zr-1Gd alloy has fine grain size and a small amount of Mg3Gd phase.When the extrusion temperature of the material is low, the grain size of the alloy is the smallest when the grain grows up to 250 鈩，

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