2A12铝合金微弧氧化膜的高温氧化性能

High-Temperature Oxidation Properties of Micro-arc Oxidation Film on 2A12 Aluminum Alloy

对2A12铝合金表面的微弧氧化膜进行了高温氧化实验研究。结果表明:微弧氧化膜层的高温抗氧化性能随着温度的升高而降低,但氧化指数均在2以上,说明微弧氧化膜层对于2A12铝合金起到了保护作用,有效地阻止了高温氧化时的氧扩散。微弧氧化膜层抗空冷热震性能要优于抗水冷热震性能,在60次热震循环后,水冷热震的合金边角处出现膜层脱落现象,而空冷热震的合金只在表面出现裂纹,没有膜层脱落现象出现。微弧氧化膜热震失效主要由膜层与基体热膨胀系数不同、膜层与H_(2)O、氧气反应分别生成氢氧化物与氧化物所导致;膜层内部的CeO_(2)起到减小孔径的作用,在热震反应初期能够有效地降低热震对膜层的影响,但随着循环次数增多,生成碱式碳酸盐和氢氧化物,导致微弧氧化膜失效。

The high-temperature oxidation experiments were conducted on the micro-arc oxidation film on 2A12 aluminum alloy surface.Results show that the high-temperature oxidation resistance of the micro-arc oxidation film is decreased with increasing the temperature.However,the oxidation index is above 2,indicating that the micro-arc oxidation film has a protective effect for the 2A12 aluminum alloy and can effectively prevent the oxygen diffusion during high-temperature oxidation.The air-cooled thermal shock resistance property of the micro-arc oxidation film layer is better than its water-cooled thermal shock resistance property.After 60 thermal shock cycles,the film falls off at the corners of alloy after water-cooled thermal shock,while only cracks appear on the surface of alloy after air-cooled thermal shock without film shedding.The failure of micro-arc oxidation film after thermal shock is mainly caused by the difference in coefficients of thermal expansion between film and substrate and the formation of hydroxides and oxides through the reactions of film with H_(2)O and oxygen,respectively.The CeO_(2) inside the film can reduce the pore size and the impact of thermal shock on the film at the initial reaction stage.However,with increasing the thermal shock cycles,the subcarbonate and hydroxide are generated,leading to the failure of micro-arc oxidation film.