生物医用可降解Zn-Cu合金力学性能和腐蚀性能的研究

发布时间：2017-12-28 08:34

本文关键词：生物医用可降解Zn-Cu合金力学性能和腐蚀性能的研究　出处：《西南交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：生物可降解金属材料由于其良好的力学性能和可生物降解性能而受到人们广泛的关注,其中镁基合金和铁基合金是研究的热点,但是由于镁合金过快的生物降解速率及铁合金过慢的降解速率难以匹配组织或机体所需,以及铁基合金腐蚀产物的生物相容性问题,限制了它们在临床上的使用。而锌具有介于二者之间的腐蚀电位,并且较均匀的腐蚀类型,使得锌有望作为新的生物可降解金属材料。目前关于可降解锌合金的研究还处于初始阶段,只有少量的文献报道。由于纯Zn弹性模量较低,作为生物可吸收材料必须将Zn合金化从而提高纯Zn的力学性能。在本文中,我们在锌中加入不同含量的Cu元素,通过熔炼制备了 Zn-xwt.%Cu(x=0,1,1.5,2,2.5)二元合金,并研究了 Cu含量变化对合金组织和性能的影响,并在此基础上通过热处理和等通道挤压工艺进一步提升材料性能,并研究了加工工艺对合金组织性能的影响。通过电化学平台及浸泡实验,本文进一步评价了 Zn-Cu合金的腐蚀行为及降解产物。研究表明,Cu元素的加入能显著提高合金的强度,随着元素含量的增加,合金产生固溶强化和第二相强化,使得强度和硬度增加。而合金伸长率随着Cu含量的增加先升高,后降低,在Cu含量为1wt%时达到最大。对Zn-1Cu和Zn-2.5Cu的等通道研究结果表明,经过等通道挤压后合金晶粒被挤碎,并且局部出现静态再结晶的细晶粒。合金的强度和塑性有很大的提升,其中Zn-2.5Cu在经过2道次的等通道挤压后抗拉强度和伸长率分别由120MPa、0.5%提高到了 220MPa、35%。经过3道次挤压后的合金与经过2道次挤压的结果相比,塑性提高,而强度下降。挤压后的试样拉伸断口形貌具有明显的韧窝特征。热处理对合金的显微组织具有较为明显的影响。其中经过300℃热处理1h后的合金晶界清晰明显,且晶粒组织更细小均匀。将经过热处理的合金进行3道次的等通道挤压,结果表明挤压前热处理有助于消除内应力,使合金变形更容易。经过300℃热处理后ECAP 3道次的样品,晶粒更均匀细小,且强度和塑性均较高,其中强度和伸长率分别为180MPa和45%。采用电化学测试和浸泡实验对Zn-Cu合金的腐蚀降解性能进行评价,结果表明,Zn及其合金具有较高的自腐蚀电位,腐蚀速率较小。随着Cu元素的加入及含量的增加,合金的腐蚀速率有所增加,但是变化较小,其中Zn-2.5Cu的腐蚀速率也仅为0.045mm/year,远低于镁合金腐蚀速率。经过等通道挤压后,Zn-Cu合金的腐蚀速率增加,快于铁基合金的腐蚀速率。浸泡实验结果表明,在SBF中浸泡一段时间的合金表面腐蚀程度较小,且腐蚀形貌较为均匀,没有出现严重的局部腐蚀。腐蚀产物的EDS结果表明,腐蚀产物主要含有P,Ca,C和O等几种元素,根据文献报道,腐蚀产物可能为磷酸盐和碳酸盐。这些结果表明,Zn-Cu合金有可能作为新型的,具有合适的降解速率的可降解金属材料。
[Abstract]:Biodegradable metallic materials due to its good mechanical properties and biodegradable properties has attracted much attention, including magnesium alloy and Fe based alloy is a hotspot of research, but because of the magnesium alloy rapid biodegradation rate and low degradation rate of iron alloy has been difficult to match the organization or body needed, and corrosion products of iron based alloy the biocompatibility problem, limiting their use in clinical practice. Zinc has a corrosion potential between the two, and a more uniform corrosion type, which makes zinc promising as a new biodegradable metal material. At present, the research on degradable zinc alloys is still in the initial stage, and only a small amount of literature is reported. Because of the low elastic modulus of pure Zn, it is necessary to allot Zn as a bioabsorbable material to improve the mechanical properties of pure Zn. In this paper, we added different content of Cu element in zinc smelting, through the preparation of Zn-xwt.%Cu (x=0,1,1.5,2,2.5) two alloy, and studied the influence of Cu content on Microstructure and mechanical properties, and on the basis of the heat treatment and ECAP process to further improve the properties of materials, and study effect of processing technology on Microstructure and properties of. The corrosion behavior and degradation products of Zn-Cu alloy were further evaluated by electrochemical platform and soaking experiment. The research shows that the addition of Cu can significantly improve the strength of the alloy. With the increase of the element content, the alloy will produce solid solution strengthening and the second phase strengthening, so that the strength and hardness will increase. The elongation of the alloy increases first and then decreases with the increase of Cu content, and reaches the maximum when the content of Cu is 1wt%. The results of the equal channel study of Zn-1Cu and Zn-2.5Cu show that the grain of the alloy is crushed after the equal channel extrusion and the fine grain of static recrystallization occurs locally. The strength and plasticity of the alloy have been greatly improved. The tensile strength and elongation of Zn-2.5Cu increased from 120MPa and 0.5% to 220MPa and 35% after 2 passes. After 3 passes of extrusion, the strength of the alloy is improved and the strength is decreased compared with the result of 2 pass extrusion. The tensile fracture morphology of the specimen after extrusion has obvious dimple characteristics. Heat treatment has an obvious effect on the microstructure of the alloy. The grain boundary of the alloy after 1h heat treatment at 300 C is clear and clear, and the grain structure is even smaller and even. The heat treated alloy is extruded at the 3 pass channel. The results show that the heat treatment before extrusion can help eliminate the internal stress and make the alloy more easily deformed. After heat treatment at 300 C, the samples of ECAP 3 pass are more uniform and finer, and the strength and plasticity are higher, and the strength and elongation are 180MPa and 45%, respectively. The corrosion and degradation properties of Zn-Cu alloy were evaluated by electrochemical test and immersion test. The results showed that Zn and its alloys had higher self corrosion potential and smaller corrosion rate. With the addition of Cu and the increase of content, the corrosion rate of alloy increases, but the change is small. The corrosion rate of Zn-2.5Cu is only 0.045mm/year, which is much lower than that of magnesium alloy. After the equal channel extrusion, the corrosion rate of the Zn-Cu alloy increases, which is faster than the corrosion rate of the iron base alloy. The soaking test results showed that the corrosion degree of the alloy immersed in SBF for a period of time was relatively small, and the corrosion morphology was even. No serious local corrosion occurred. The EDS results of corrosion products show that the corrosion products mainly contain several elements such as P, Ca, C and O. According to the literature, the corrosion products may be phosphate and carbonate. These results show that Zn-Cu alloy may be a new type of degradable metal material with suitable degradation rate.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG146.13;R318.08

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