脉冲电流宽度对镁合金微弧氧化过程的影响

Effect of Current Pulse Width on Micro-arc Oxidation for Magnesium Alloys

摘要:

为了揭示脉冲电流宽度对AZ31B镁合金微弧氧化过程的影响规律，利用示波器记录电流波形，借助涡流测厚仪测量陶瓷层厚度，采用扫描电子显微镜观察陶瓷层表面和截面形貌，根据电压变化曲线计算微弧氧化过程能量消耗。结果表明，随着脉宽由15 μs增至90 μs，起弧时间由358 s缩短至25 s，起弧电压先降低后升高并在脉宽30 μs时达到最小值183 V；陶瓷层表面放电微孔孔径增大，微孔数量减少，陶瓷层厚度增加但致密度下降；起弧过程能量消耗随脉宽增大先降低后升高，并在脉宽为30 μs时达到最小值3.9 kJ；陶瓷层生长过程能量消耗随脉宽增大近似成倍增加；单位厚度陶瓷层的生长能耗先降低后平稳增长，同样在脉宽30 μs时达到最小值10.2 kJ

Abstract:

The effects of current pulse width on Micro-arc Oxidation (MAO) process for AZ31B magnesium alloys were investigated using pulse power source. The pulse shapes were recorded by an oscillograph. The thickness of MAO coat was measured by an eddy current thickness gauge. The surface and cross section morphologies of MAO coat were observed by scanning electron microscope (SEM). The energy consumption of MAO process was calculated by curves of voltage-time. The results indicate that with current pulse width increasing from 15 μs to 90 μs, the arcing time during MAO process shortens from 358 s to 25 s, the arcing voltage first drops and then increases. When pulse width is 30 μs, the arcing voltage reaches the minimum value of 183 V. The pore diameter of Millipore is enlarged but the quantity is reduced. And the thicker ceramic coat is obtained on Mg samples but the density of MAO coat is decreased. The energy consumption of arcing process is decreased at first and then raised with increasing of pulse width, and the minimum value is 3.9 kJ when pulse width is 30 μs. The energy consumption of MAO coat growing process is nearly of fold increase with increasing of pulse current. The energy consumption per thickness of MAO coat drops firstly and then rises stably, and the minimum value is 10.2 kJ when pulse width is 30 μs.