【作者】 宋少杰；

【导师】 熊金平；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2010， 硕士

【摘要】 本文采用恒电位极化、动电位极化和交流阻抗等方法,研究了NiTi合金在模拟人体液中Em和Eb的分布；氯离子浓度,温度,电位对亚稳态孔蚀特征参数的影响；电位,氯离子浓度,表面粗糙度及pH值对NiTi合金阻抗普图的影响；并结合304不锈钢在含氯离子环境中的Em、Eb值,亚稳孔个数,亚稳孔生长速度,峰值电流等特征,对比NiTi合金的亚稳态孔蚀特征,进一步揭示NiTi合金亚稳态特征的内在原因。随着电位,氯离子浓度的不断升高,NiTi合金的Em、Eb均减小,亚稳孔形核数目和平均峰值均呈增大趋势。但随着温度的升高,NiTi合金在钝化区内形成的亚稳孔的数目呈现减弱的趋势。电位的升高,NiTi合金的阻抗值减小；当电位超过NiTi合金的点蚀电位时,电化学阻抗谱上出现Warburg阻抗。氯离子浓度的升高,NiTi合金的阻抗值减小。粗糙表面有利于亚稳态的形核并促进孔的生长。无论在酸性溶液还是碱性溶液中,随着溶液酸碱程度的增加,NiTi合金的钝化能力均呈减弱趋势。NiTi合金的蚀孔容易沿着划痕的方向生成。304不锈钢亚稳孔寿命随着电位提高有减小的趋势。一般情况下,304不锈钢亚稳态小孔的Ⅰ值和平均生长速度k值都比较小,孔半径和峰值电流都很小,二者没有明显的线性关系。孔平均生长速度与孔半径的分布满足正态分布。NiTi合金的钝化性和耐蚀能力均优于304不锈钢。在整个钝化区范围内304不锈钢的受电位的影响较大,电流较高,其亚稳孔更容易发展成稳定孔；NiTi合金则产生了多而密的亚稳态小孔,能在高电位下持续再钝化。更多还原

【Abstract】 Potentiostatic and potentiodynamic polarization methods were employed to study the behavior of metastable pitting on NiTi alloy in PBS. This study contained the distribution of Em and Eb research; influence research of Cl" concentration, temperature and electode to metastable characters; influence research of electode, Cl" concentration, suface roughness and pH value to the impedence; and also studied the metastable pitting parameter of 304 stainless steel, such as Em, Eb, number, current, growth speed of metastable pitting, to compare with NiTi alloy’s for the internal reasons of NiTi alloy metastable pitting.With the growth of electrode and Cl- concentration, the Em, Eb, number, peak current of the NiTi alloy reflected a diminish trend. But when the temperature went up, the number of metastable pitting had decreased.The electrode went up, the impedence of NiTi alloy went down. But when the potential had come across the Eb, there was Warburg impedence on the impendence curves. Rough suface was better for holes growing. Either in acid solution or in alkai liquid, the passivation capacity of NiTi alloy had weakened. Metastable pitting easily occurred along the direction of nick.The metastable pitting life of NiTi alloy diminished, while potential enhanced. Generally speaking, metastable I and k value were small, and there was no linear relationship between the two. The distribution of I and k value contented a normal distribution.The passivation and anticorrosion capacity of NiTi alloy were much better than 304 stainless steel’s. During the passivation area of 304 steel, the electrode influence to the steel were bigger than NiTi alloy. Under high potential, plenty of metastable pitting were found on the suface of NiTi alloy and could repassivated, while the metastable pitting tent tobecome stable pitting.更多还原