基于COMSOL的微弧氧化过程温度场分布研究

目的研究微弧氧化过程的温度场分布情况对成膜过程及表面形貌的影响。方法以7075铝合金微弧氧化过程中的一个放电通道为研究对象,基于多物理场仿真软件COMSOL Mutiphysics建立了微弧氧化传热过程的数学模型及物理模型。基于有限元法求解出微弧氧化成膜过程的温度场分布,选择特定参考线及参考点,绘制了温度-时间曲线。选择0、100、500、1000μs四个关键时间点,绘制了对应的温度-纵向深度曲线、温度分布云图及温度梯度分布云图,并探究其对陶瓷层表面形貌的影响。结果在0~100μs时,放电通道区域温度下降速率最快;在100~500μs时,温度下降速率逐渐减小;在500~1000μs时,温度下降速率最小且趋于不变。相对于放电通道中心区域,靠近氧化铝膜层-铝合金基体界面区域温度下降速率较快,温度梯度较大;在0、100、500、1000μs时,最高温度所在位置的纵向深度依次为93、20、26、38μm,呈现先减小后增大的趋势。结论电解液对微弧氧化过程的冷却作用主要集中于放电通道形成后的100μs内。除电解液外,氧化铝膜层-铝合金基体界面在微弧氧化成膜过程中有一定的冷却作用,而放电通道各区域冷却速率不均衡是氧化膜表面形成火山口状孔洞的主要原因。

Temperature Field Distribution of Micro-arc Oxidation Process Based on COMSOL

The work aims to study effects of temperature field distribution during micro-arc oxidation process on film for-mation process and morphology. With a discharge channel of 7075 aluminum alloy as object of study, a mathematical model and a physical model were established for micro-arc oxidation heat transfer process based on the multi-physics simulation software COMSOL Mutiphysics. The temperature field distribution of the micro-arc oxidation film forming process was solved in finite element method. Some specific reference lines and reference points were selected to plot temperature-time curve; key time points including 0, 100, 500, 1000 μs were selected to plot temperature-longitudinal depth curve, temperature distribution chart and temperature gradient distribution chart. Their effects on morphology of the ceramic layer were investigated as well. In 0~100 μs, temperature of the discharge channel region decreased at the fastest speed; in 100~500 μs, the temperature descending rate decreased gradually; in 500~1000 μs, the temperature drop rate was the smallest and tended to be constant; compared with that in the discharge channel central area, temperature drop was faster and the temperature gradient was larger near alumina film-aluminum alloy interface; at 0, 100, 500, 1000 μs , longitudinal depth of the maximum temperature position was 93, 20, 26, 38 μm, tending to decrease first and increased later. Cooling effect of the electrolyte on the micro-arc oxidation process is main-ly present within 100 μs after the discharge channel takes shape; in addition to the electrolyte, the alumina-aluminum alloy in-terface has also played a certain role during this process, and unbalanced cooling rate in each area of the discharge channel is the main cause of formation of the crater-like holes on the oxide film surface.