过热浆铸7075铝合金的阳极氧化工艺参数

摘要

通过对过热浆铸7075铝合金基体阳极氧化工艺参数包括电压、电流密度、温度和电解液的选择,确定合适的阳极氧化工艺参数.该合金阳极氧化所用溶液为硫酸电解液、硫酸与硼酸或柠檬酸的混合液.阳极氧化所用电压为15～30 V,测试电流密度为2和3 A/dm2,温度为5和15℃.测试氧化膜的厚度、表面形貌、硬度和耐腐蚀性.结果发现,该合金在硫酸溶液中阳极氧化的最佳参数为25 V、2 A/dm2和5℃.此条件下形成的氧化膜表面光滑且厚度均一、孔隙率低、硬度高,且具有最优的耐腐蚀性.然而,在较高温度(15℃)下进行阳极氧化时,可以观察到不连续的氧化膜.所用替代电解质是硫酸与硼酸或柠檬酸的混合溶液.结果表明,硼酸和柠檬酸电解液均能提高氧化膜的厚度、硬度、耐蚀性和品质.但是,这些氧化膜的性能仍然比不上合金在硫酸电解液中低温下(25 V,2 A/dm2,5℃)形成的氧化膜的性能.%The anodizing parameters of voltage, current density, temperature, and electrolyte choice were assessed to find an appropriate combination for the superheated slurry cast 7075 Al alloy substrate. The alloy was anodized in sulfuric acid electrolyte or alternatively in sulfuric acid mixed with boric acid or citric acid. The voltages applied were in the range of 15?30 V. Anodizing current densities tested were 2 and 3 A/dm2, while temperatures tested were 5 and 15 ℃. Thickness, surface morphology, hardness, and corrosion resistance of the oxide film were then evaluated. It was found that 25 V, 2 A/dm2 and 5 ℃ were suitable for this alloy when anodized in sulfuric acid. The oxide film was smooth with uniform thickness, low porosity, high hardness, and had the highest corrosion resistance at these parameters. However, discontinuous oxide films were observed from samples anodized at higher temperature of 15 ℃. Alternative electrolytes considered were sulfuric acid mixed with boric acid or citric acid. The results showed that electrolytes with boric acid or citric acid increased thickness, hardness, corrosion resistance and quality of the oxide films. However, these oxide films were inferior to those obtained with sulfuric acid electrolyte at lower temperature (25 V, 2 A/dm2 and 5 ℃).