7A09铝合金阳极化膜层颜色异常原因分析

Analysis on Abnormal Color of Anodizing Film on 7A09 Aluminum Alloy

某7A09铝合金壳体阳极化膜颜色异常。为此,通过形貌观察、能谱分析及硬度测试等手段对其原因进行了分析。结果显示:壳体阳极化后表面局部发黑,发黑的区域对应原始棒材的心部区域、沿纵向连续分布;发黑的原因是由于该区域存在成分偏析(Zn合金含量高)和化合物富集,导致该区域的晶粒尺度比正常区域小、耐蚀性比正常区域略差,在阳极化时该区域优先反应,阳极化后该区域膜层颜色出现异常。

The color of anodizing film on a 7 A09 aluminum alloy shell was abnormal.Therefore,the reason was analyzed by means of morphology observation,energy spectrum analysis and hardness test.Results showed that the surface of the shell after anodizing was locally blackened,and the blackened area corresponded to the central region of the original bar and was continuously distributed along the longitudinal direction.The reason for blackening was the existence of component segregation(high content of Zn alloy)and compound enrichment in this area,which led to the decrease of the grain size and the slightly worse corrosion resistance of the area.Therefore,during anodizing the reaction in this area was preferential and the color of film in this area appeared abnormal after anodization.