高压扭转超细晶纯钛腐蚀行为研究

发布时间：2018-05-09 10:02

本文选题：腐蚀行为 + 微观组织　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：在过去的十年里,材料科学领域中,纳米材料成为了最热门的方向之一,同时也展现出了其作为功能材料使用极好的发展前景。例如,由具有纳米级别尺寸的纯钛替代了由Ti-4Al-6V合金制成的小直径牙科植体,纳米钛不仅增加了其机械强度和疲劳寿命,同时还表现出了良好的生物相容性,这使得超细晶材料在应用层面得到了广泛的认可。因此,超细晶材料在微成形技术领域上的普及应用将成为微制造方向发展的主要目标之一。纯钛拥有优秀的生物相容性及耐腐蚀性能,是最优潜力的医用金素材料。但由于耐磨性差和强度较低导致其作为生物植入体受到了限制,而超细晶制备工艺所对应的组织细化效果可以有效地提高纯钛的力学性能从而打破该方面的限制。本课题选用先进的高压扭转技术(HPT)制备超细晶纯钛,通过开路电位、极化曲线和交流阻抗谱等电化学测量方法,结合透射电镜进行显微组织观察(TEM)以及扫描电镜进行表面形貌分析(SEM),研究了HPT变形工艺制备的超细晶纯钛在硫酸溶液和模拟体液两种环境中的腐蚀行为。本文对工业纯钛进行了不同转数的高压扭转实验,研究了不同变形程度制备超细晶工业纯钛的显微组织变化规律和晶粒尺寸的变化规律。结果表明:高压扭转变形工艺处理0.25t时,待加工试样晶粒因受到剪切应力而出现扭转变形进而导致晶粒内部出现大量孪晶和位错,此时晶粒尺寸仍然较大。1t时,晶粒尺寸未明显减小,显微组织由滑移带和位错缠结、位错胞等位错亚结构组成;5t时,晶粒细化到0.3μm左右,微观组织由细小的位错胞状和亚微米级晶粒组成。10t时,晶粒发生明显细化,平均晶粒尺寸在150nm左右,晶粒已经明显细化,组织均匀性较好。同时随着扭转圈数增加,超细晶纯钛的显微硬度随之提高,5t和10t试样的显微硬度已超过Ti-4Al-6V合金。研究了不同退火处理超细晶纯钛的显微组织,实验结果表明:200℃退火时超细晶纯钛位错数量减少但晶界仍然处于非平衡态;400℃退火时不平衡的组织出现回复现象但晶粒尺寸相差较大,且没有再结晶形核阶段;此时内部的位错缠结区所占比例很大;600℃退火时出现再结晶,位错密度逐渐降低,晶粒内的内应力也逐渐降低;微观组织主要以等大、均匀且细小的等轴亚微米晶粒构成。HPT变形工艺制备的超细晶纯钛在硫酸溶液的研究表明,抗腐蚀性能均低于原始粗晶钛;但随着扭转圈数的增加,抗腐蚀性能得到了回升。0.25t制备的超细晶试样抗腐蚀性能最差,10t制备的超细晶试样抗腐蚀性能最好。不同退火温度处理的超细晶纯钛,随着退火温度的升高,抗腐蚀性能随之提升;600℃退火保温0.5小时处理下耐蚀性最佳,腐蚀电流密度出现明显降低,表面腐蚀产物分布最为均匀,致密性也最好。原始钛和超细晶纯钛在硫酸溶液中的钝化膜成分TiO_2。在模拟体液的腐蚀环境中的研究结果表明,无论原始钛还是超细晶纯钛,腐蚀主要发生在晶界处但原始钛的耐蚀性最佳。不同扭转圈数处理的HPT超细晶纯钛,随着扭转圈数的增加,腐蚀电位正向移动,腐蚀电流大幅度减小,交流阻抗谱的高频容抗弧半径增大,低频相角升高,拟合的钝化膜电阻也明显增大,耐腐蚀性得到充分改善;不同退火温度处理的超细晶纯钛在模拟体液环境中,随着退火温度的升高,抗腐蚀性能随之提升;600℃退火保温0.5小时条件处理下耐蚀性最佳。
[Abstract]:In the past ten years, nanomaterials have become one of the hottest fields in the field of material science, and they have also shown excellent prospects for use as functional materials. For example, a small direct diameter dental implant made from Ti-4Al-6V alloy has been replaced by pure titanium with nanoscale size. The nano titanium not only increases the mechanical strength of the dental implant. The degree and fatigue life also show good biocompatibility, which makes the ultrafine crystal materials widely recognized at the application level. Therefore, the popularization and application of ultrafine crystalline materials in the field of micro forming technology will be one of the main goals of the development of micro manufacturing direction. Pure titanium has excellent biocompatibility and corrosion resistance. It is the best potential medical gold material. However, because of poor wear resistance and low strength, it is restricted as a biological implant, and the microstructure refinement effect of the ultrafine crystal preparation process can effectively improve the mechanical properties of pure titanium and break the limitation of this aspect. This topic selects the advanced high pressure torsion Technology (HPT) system. Ultrafine crystal pure titanium was prepared by means of open circuit potential, polarization curve and AC impedance spectroscopy. The microstructure observation (TEM) and scanning electron microscope (SEM) were carried out by transmission electron microscopy (TEM). The corrosion behavior of ultrafine crystal pure titanium prepared by HPT deformation process in two environments of sulfuric acid solution and simulated body fluid was studied. In this paper, the high pressure torsion test of industrial pure titanium was carried out with different rotation numbers. The change law of microstructure change and grain size of ultrafine crystal industrial pure titanium were studied with different deformation degree. The results showed that when the high pressure torsion deformation process was treated with 0.25t, the grain of the sample to be processed was torsional deformation because of shear stress. A large number of twins and dislocations are found inside the grain, and when the grain size is still larger.1t, the grain size does not decrease obviously, and the microstructure is composed of dislocation substructures, such as slip band and dislocation entanglement and dislocation cell. When 5T, the grain is refined to about 0.3 m, and the microstructure is made up of fine dislocation cell and submicron grain.10t. The average grain size is about 150nm, the grain size is about 150nm, the grain size is refined and the microstructure uniformity is better. At the same time, the microhardness of the ultrafine crystal pure titanium increases with the number of twisting rings, and the microhardness of the 5T and 10t samples has exceeded that of the Ti-4Al-6V alloy. After annealing at 200 c, the number of dislocation of pure titanium is reduced but the grain boundary is still in the nonequilibrium state, and the imbalance of the structure at 400 C appears to be reversion, but the grain size varies greatly, and there is no recrystallization stage. At this time, the dislocations in the internal dislocations occupy a large proportion, and the recrystallization occurs at 600 C, and the dislocation density decreases gradually. The internal stress in the grain is lower, and the microstructure of the microstructures is mainly composed of equal, uniform and fine submicron grain in the.HPT deformation process. The study of the ultrafine crystal titanium in the sulfuric acid solution shows that the corrosion resistance is lower than the original coarse grain titanium, but with the increase of the number of torsion rings, the corrosion resistance has been recovered by.0.25t. The ultra-fine crystal specimens have the worst corrosion resistance. The ultra-fine crystal samples prepared by 10t have the best corrosion resistance. The corrosion resistance of ultrafine crystalline titanium treated with different annealing temperatures increases with the increase of annealing temperature. The corrosion resistance is best under annealing at 600 C for 0.5 hours, the corrosion current density decreases obviously, and the surface corrosion products are divided. The original titanium and ultrafine pure titanium in the sulfuric acid solution, TiO_2., in the corrosion environment of the simulated body fluid, showed that the corrosion mainly occurred at the grain boundary, but the corrosion resistance of the original titanium was the best. The HPT ultrafine crystal treated with different torsional rings was pure. With the increase of the number of torsional rings, the corrosion potential is moving forward, the corrosion current is greatly reduced, the high frequency resistance arc radius of the AC impedance spectrum increases, the low frequency angle increases, the resistance of the fitted passivation film also increases obviously, and the corrosion resistance is fully improved; the ultrafine pure titanium treated with different annealing temperatures is retreated in the simulated body fluid environment. The corrosion resistance increased with the increase of fire temperature. The best corrosion resistance was obtained when annealing at 600 C for 0.5 hours.

【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG178

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