微弧氧化对镁合金丝材性能和微观组织的影响研究

发布时间：2018-01-05 22:07

本文关键词：微弧氧化对镁合金丝材性能和微观组织的影响研究　出处：《东南大学》2015年硕士论文　论文类型：学位论文

【摘要】：镁合金是一种应用前景广阔的可降解生物医用材料,通过表面处理可以弥补其在生理环境中腐蚀过快的缺点。本文采用微弧氧化技术对AZ31B镁合金丝材进行表面改性处理,研究了氧化时间和电流密度等微弧氧化工艺参数对镁合金丝性能和微观组织的影响,在此基础上,系统研究了微弧氧化时间、磷酸缓冲液中氯离子浓度以及PLLA封孔处理对镁丝降解性能的影响规律,研究表明：镁合金丝表面微弧氧化膜的组成相以MgO为主,延长氧化时间,陶瓷膜表面裂纹增多,膜层孔隙率先增大后减小,氧化时间为30min (10-30min)时孔隙率最大,而氧化时间对膜层表面孔隙大小没有明显影响；增大电流密度,微弧氧化膜生长速率呈线性上升,表面裂纹增多,孔隙率和平均孔径均先增大再减小,电流密度为8A/dm2(6-108A/dm~2)时两者达到最大值,分别为6.4%和2.59μm。延长氧化时间或增大电流密度都会增加膜层厚度,降低抗拉强度。丝材直径对镁合金微弧氧化陶瓷膜的微观组织影响不大,但膜层孔隙率和平均孔径随丝径增大而减小,丝材强度损失率随之降低。微弧氧化处理会导致小丝径的镁合金丝平均晶粒尺寸略有增大。微弧氧化处理能显著提高镁丝在含血液浓度氯离子的磷酸缓冲液中的耐腐蚀性。短时间浸泡(低于10天),微弧氧化时间的影响不大；浸泡10天后,10min氧化处理的镁丝剩余质量百分数最大。浸泡10天,光丝表面腐蚀严重,而10min氧化处理镁丝表面陶瓷层保持完整。浸泡4天后,10min氧化镁丝的剩余抗拉强度最大,光丝的强度损失率最大。不同浓度氯离子的磷酸缓冲液浸泡实验发现,浸泡相同时间,磷酸缓冲液中氯离子含量越大,镁丝裂纹越多,抗拉强度损失率增大。PLLA涂覆处理后,微弧氧化时间对镁丝浸泡过程中的质量和直径损失率影响小。浸泡33天时,20min和30min氧化并经PLLA涂覆处理的两种镁合金丝表层均保持完整,后者剩余抗拉强度最大。
[Abstract]:Magnesium alloy is a promising biodegradable biomedical material. Surface treatment can make up for the shortcomings of rapid corrosion in physiological environment. In this paper, the surface modification of AZ31B magnesium alloy wire was carried out by using micro-arc oxidation technology. The effects of oxidation time and current density on the properties and microstructure of magnesium alloy wire were studied. The effect of chloride concentration in phosphate buffer solution and PLLA sealing treatment on the degradation performance of magnesium wire was studied. The results showed that the composition of micro-arc oxide film on magnesium alloy wire surface was mainly composed of MgO and the oxidation time was prolonged. When the surface crack of ceramic membrane increases, the porosity of the film increases first and then decreases, and the porosity is the highest when the oxidation time is 30 min or 10 ~ (-30 min). However, the oxidation time has no obvious effect on the pore size of the film surface. With the increase of current density, the growth rate of micro-arc oxide film increases linearly, the surface cracks increase, and the porosity and average pore size increase first and then decrease. When the current density is 8A / dm ~ (2) 6-108A / d ~ (2), the maximum value is 6.4% 渭 m and 2.59 渭 m, respectively. Increasing the oxidation time or increasing the current density will increase the film thickness. The decrease of tensile strength. The wire diameter has little effect on the microstructure of magnesium alloy micro-arc oxidation ceramic film, but the film porosity and average pore size decrease with the increase of wire diameter. The average grain size of the magnesium alloy wire with small wire diameter increased slightly after microarc oxidation treatment. The microarc oxidation treatment could significantly increase the magnesium wire in the phosphate buffer solution containing chlorine ion in blood concentration, and the average grain size of the magnesium alloy wire with small wire diameter was slightly increased by micro-arc oxidation treatment, which resulted in a slight increase in the average grain size of magnesium alloy wire. Corrosion resistance-soaking for short periods (. Less than 10 days. The effect of the time of micro-arc oxidation is not significant. After soaking for 10 days, the residual mass percentage of magnesium wire treated by oxidation for 10 minutes was the largest, and the surface corrosion was serious after soaking for 10 days. However, the ceramic layer on the surface of the magnesium wire treated by oxidation for 10 minutes remained intact, and the residual tensile strength of the magnesium oxide wire was the highest after immersion for 4 days. The strength loss rate of light filament is the biggest. The experiment of immersion in phosphate buffer with different concentration of chloride ion shows that the more chlorine ion content in phosphate buffer solution, the more cracks in magnesium wire. The effect of microarc oxidation time on the quality and diameter loss rate of magnesium wire during immersion was little after the increase of tensile strength loss rate. After 33 days of immersion, the microarc oxidation time had little effect on the quality and diameter loss rate of magnesium wire. The surface layers of the two magnesium alloy wires, which were oxidized for 20min and 30min and coated with PLLA, remained intact, and the residual tensile strength of the latter was the largest.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG174.4;TG146.22

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