为了研究激光冲击对镁合金表面抗腐蚀性能的影响, 利用钕玻璃脉冲激光对AZ31镁合金表面进行不同次数的激光冲击处理, 用透射电子显微镜观察镁合金表层的微观组织, 并采用电化学测量技术在氯化钠溶液(质量分数为0.035)中测试其极化曲线和电化学交流阻抗谱的影响。结果表明, 激光冲击波导致镁合金表面层产生超高应变速率的塑性变形; 晶粒内部存在与孪晶相互交叉、相互缠结的高密度位错而导致晶粒细化; 极化曲线和交流阻抗谱表明1次激光冲击后AZ31的自腐蚀电位提高约267mV;腐蚀电流稍有增大, 反应电阻增大, 抗腐蚀性明显提高; 随着冲击次数的增多, 腐蚀抗力未明显提高。其相应的交流阻抗谱也得出与极化曲线相同的结论。该研究对于激光冲击处理镁合金提高耐腐蚀性具有一定的参考价值。

In order to study effect of laser shock times on corrosion resistance of AZ31 magnesium alloy, AZ31 magnesium alloy was processed at different laser shock process (LSP)times by Nd∶glass laser with pulse width of 23ns. Microstructures were observed by transmission electron microscopy. Polarization curves and electrochemical impedance spectroscopy were obtained in NaCl solution with 0.035 mass fraction by means of electrochemical measurement technique. The results show that plastic deformation with ultrahigh strain rate happens because of laser shock wave at the surface layer of AZ31 magnesium alloy. High density dislocations with intersect and entanglement of twin crystal exist in the crystal grains and the dislocations led to grain refinement. Polarization curves and electrochemical impedance spectroscopy shows that corrosion potential of AZ31 increases up to 267mV after the first laser shock. Corrosion current increases slightly, reaction resistance increases and corrosion resistance is improved significantly. With the increase of impact times from LSP, corrosion resistance of alloy is not improved significantly. The corresponding impedance spectroscopy has the same conclusion with polarization curves. The study is helpful for improving the corrosion resistance of magnesium alloy during laser shocking processing.