7075铝合金锻件氧化黑斑分析

Analysis of oxidation“black spot”of 7075 aluminum alloy forgings

采用低倍、高倍组织观察、成分分析等方法研究传动支架用7075铝合金锻件硫酸阳极氧化膜颜色发黑缺陷的原因及形成机理。结果表明,锻件成分偏析和淬透性差共同作用导致淬火时效后锻件不同位置析出的数量出现差异,阳极氧化过程中,强化相析出量多、尺寸较大的位置,因可溶强化相会造成氧化膜中的大量细小孔洞,使阳极氧化膜颜色发黑显现为黑斑。

The reasons and formation mechanism of the blackening defect of sulfuric acid anodized film on 7075 aluminum alloy forgings for transmission brackets were studied using low magnification and high magnification structure observation,composition analysis,and other methods.The results show that the combined effect of component segregation and poor hardenability of forgings lead to the difference in the amount of precipitation at different positions of forgings after quenching and aging.In the process of anodic oxidation.During the anodizing process,the areas with more precipitation and larger size of strengthening phases caused a large number of small pores in the oxide film due to soluble strengthening phases,resulting in blackening of the anodic oxide film color as black spots.