微弧熔区的淬冷过程及其对氧化铝膜微观结构的影响

Simulation of Quenching Process during Microarc Oxidation (MAO) and its Effect on the Microstructure of Al_2O_3 Coating

通过实验和模拟拟合,对微弧氧化过程中Al_2O_3膜表面的对流散热系数作了估计,实验过程中发现Al_2O_3/Al界面在微观上也是一个冷却界面,Al基体在冷却过程中起"热量中转"的作用,熔池在淬冷过程中的大部分热量经过了邻近区域的Al_2O_3膜或者铝基体.通过热模拟得到的纵深各点温度-时间曲线来表征微熔区的淬冷过程.通过对各节点的相对冷却速度比较,阐述了淬冷过程对α-Al_2O_3分布和Al_2O_3膜表面形貌的影响,压力因素在微观结构形成过程中所产生的影响作了粗略的分析.

The convection heat transfer coefficient on Al2O3 coating during microarc oxidation process was estimated by experiment and simulation. The Al2O3/Al interface was found to be a heat- transfer passage. During quenching, most heat of the micro-melting-pool was transferred through the Al substrate and the Al2O3 coating nearby. The micro-melting-pool was modeled by the finite element method （FEM）, and the process of quenching was characterized by the simulated temperature-time curves of the nodes along the depth, respectively. The effects of the quenching on the distribution of α-Al2O3 and surface morphology of Al2O3 coating were discussed by comparing the relative cooling rate at different positions. The influence of pressure on the microstructure of Al2O3 coating was also discussed briefly.