硅酸钠浓度对铝合金微弧氧化起弧过程能量消耗的影响

摘要

The arcing process of micro­arc oxidation (MAO) on 1015 alloys aluminum (Al) using pulse power source in aqueous solutions with different Na2SiO3 concentrations was studied. The morphologies and surface resistance of initial films at arcing moment were analyzed and observed using scanning electron microscope (SEM) and electrochemical test, respectively. The effect of Na2SiO3 concentration on energy consumption of arcing process during MAO was calculated based on change curve of voltage. The results indicate that there is no arcing phenomenon but electrolytic etching on Al samples when the Na2SiO3 concentration is 0 and voltage is 1 500 V. With Na2SiO3 solution concentration increasing from 0.25 g/L to 10 g/L, arcing voltage dropping from 1 217 V to 351 V, arcing time reducing from 270 s to 40 s , the quantity of microspores on surface of initial films increases during arcing process of MAO. The high resistance film with resistance up to 105 order of magnitude formed on the surface of Al samples is the premise of arcing phenomenon emerging in MAO process, and higher Na2SiO3 solution concentration is beneficial to forming high resistance film. The energy consumption of arcing process is diminished with Na2SiO3 solution concentration increasing, and minimum value is 16 kJ/dm2 when Na2SiO3 concentration is 10 g/L.%　　利用脉冲微弧氧化电源研究1015铝合金于不同浓度硅酸钠水溶液中的起弧过程，借助扫描电子显微镜和电化学测试方法分析硅酸钠浓度对起弧瞬间膜层微观结构和表面阻值的影响，并根据电压变化曲线计算起弧过程的能量消耗。结果表明：当溶液中硅酸钠浓度为0时，即使极间电压升至1500 V，铝合金表面仍无微弧放电现象出现，并发生电解腐蚀；随着硅酸钠浓度由0.25 g/L 增加至10 g/L 时，铝合金表面发生微弧放电现象所需的电压由1217 V 降低至351 V，通电至起弧的等待时间由270 s 缩短至40 s，起弧瞬间膜层表面放电微孔数量增多；铝合金表面形成阻值达105数量级的高阻抗膜是发生微弧放电现象的前提，硅酸钠浓度的增大有利于形成高阻抗膜；铝合金微弧氧化起弧过程的能量消耗随着电解液中硅酸钠浓度的增大而减小，并在硅酸钠浓度为10 g/L 时达到最小值，仅为16 kJ/dm2。