采用自主构建的体外模拟流场环境实验平台,通过电化学阻抗谱(EIS)测量、拉伸实验、模拟体液pH值变化测试、SEM观察等方法,对AZ31镁合金在流场环境中的腐蚀行为进行了研究。从腐蚀电化学角度探究了流场中镁合金腐蚀速率与流速的定量关系,并采用ANSYS有限元分析研究了流态与剪切力作用对镁合金不同部位腐蚀差异的影响。结果表明,流场会加速AZ31镁合金的腐蚀,在腐蚀初期,腐蚀电流密度i_corr与流场平均流速ν之间存在\begin{array}{c}{i_{\mathit{corr}}}^{-1}={i_c}^{-1}+A{\nu }^{-1/2}\end{array}的关系,其中,i_c为不考虑扩散影响时的腐蚀电流密度,A为常数。腐蚀速率随流速增加而增大,且随着腐蚀时间延长,由于腐蚀产物的影响而逐渐偏离i_corr^-1~ν^-1/2的线性关系。有限元分析表明,样品不同部位表面流体流态及剪切应力分布不同,局部传质系数K存在显著差异,不同流速下试样边缘部位的传质系数是中间的4~5倍,试样局部腐蚀形貌与剪切应力分布及流态差异相对应。

Magnesium alloy is now a promising bio-absorbable material. The previous researches on the corrosion and degradation behavior of biomedical magnesium alloy are mainly carried out in static conditions in vitro. However, considering the real physiological flow field of different flow states in vivo, the static degradation experiments can not effectively simulate the real situation. It is important to study the effect of flow field on the corrosion behavior of magnesium alloy and establish the relationship between flow rate and corrosion rate for the research and development of biomedical magnesium alloy. The corrosion behavior of AZ31 magnesium alloy in the flow field was studied using a self-designed dynamic test bench in vitro by electrochemical measurement, tensile method, pH value test of simulated body fluid (SBF) and SEM observation in this work. The relationship between the corrosion rate of magnesium alloy and the flow rate of the flow field was investigated from the perspective of corrosion electrochemistry. The influence of flow state and flow-induced shear stress (FISS) on corrosion behaviors at different positions of magnesium alloy was also studied by ANSYS finite element analysis. The results show that the flow field will accelerate the corrosion of AZ31 magnesium alloy and the corrosion rate increases with the increase of the flow rate. There is a relationship between the corrosion current density i_corr of magnesium alloy and the average flow rate ν during the early corrosion stage, namely \begin{array}{c}{i_{\mathit{corr}}}^{-1}={i_c}^{-1}+A{\nu }^{-1/2}\end{array}, where i_c is the corrosion current density ignoring the influence of diffusion, and A is a constant. With the corrosion time extended, due to the influence of the corrosion products, the experimental results gradually deviate from the calculated linear relationship of i_corr^-1~ν^-1/2. Also, there are significant differences in the fluid flow state and FISS distributions at different positions of the sample. The mass transfer coefficient at the edge of the sample under different flow rates is 4~5 times bigger than that at the middle position. The localized corrosion morphology corresponds well to the FISS distribution and the difference of flow state.