某2D70铝合金筒形件阳极氧化膜颜色异常分析

Abnormal Color Analysis of Anodized Oxidation Film of a 2D70 Aluminum Alloy Cylindrical Part

针对某2D70铝合金筒形件表面阳极氧化膜颜色异常发白的缺陷,利用光学显微镜、扫描电子显微镜、透射电子显微镜和电导率仪等研究了基体及氧化膜的显微组织、微区成分、析出相和电导率,分析了其颜色异常发白的原因。结果表明:该筒形件部分区域在时效过程中因温度过高而导致析出相异常长大,在阳极化过程中粗大析出相使该区域内电流密度发生波动,导致膜层致密程度与周围正常区域的差异较大而引起反光能力不同,致使颜色异常发白;可在进行时效等热处理时采取悬挂等措施以避免局部温度过高。

Aiming at the abnormal white color defect of anodized oxidation film on the surface of a 2D70 aluminum alloy cylinderical part,the microstructure,micro-area composition,precipitation and the conductivity of the matrix and the oxidation film were studied by the optical microscope,scanning electron microscope,transmission electron microscope and conductivity meter and the reason for the abnormal white color was analyzed.The results show that the precipitations in some areas of the cylindrical part grew abnormally due to the high temperature during the ageing process.These coarse precipitations resulted in the current density fluctuation in these areas during the anodized oxidation process,leading to the different relative density of the film from that of the surrounding normal areas.The different relative density caused the different ability of the reflecting power,leading to the abnormal white color.Some measures such as hanging the parts during the ageing treatment can be adopted to avoid the partially high temperature.