2060铝锂合金在3种溶液体系中所得阳极氧化膜层的性能

摘要

分别采用硼硫酸(45.0 g/L硫酸+8.0 g/L硼酸)、硫酸(160.0 g/L硫酸)和混酸(140.0 g/L硫酸+20.0 g/L草酸+50.0 g/L酒石酸钾钠+1.5 g/L添加剂)这3种溶液体系在2060铝锂合金上制备阳极氧化膜,考察了电流或电压对所得膜层性能的影响.用金相法测量了氧化膜的厚度,用扫描电镜观察了氧化膜的微观形貌.通过静力拉伸及拉?拉疲劳试验测试了阳极氧化前后铝锂合金的力学性能.通过观察疲劳断口的形貌,分析了阳极氧化工艺影响铝锂合金疲劳性能的原因.2060铝锂合金在3种体系中均能形成颜色均一、表面光滑的阳极氧化膜.在硼硫酸体系中得到的阳极氧化膜厚度不足2 μm,在硫酸和混酸体系中得到的阳极氧化膜的厚度可达15 μm.阳极氧化工艺显著提升了铝锂合金的耐蚀性,在混酸、硫酸和硼硫酸体系中得到的阳极氧化膜的耐中性盐雾时间依次为870、378和87 h,远超纯铝锂合金的8 h.但是,混酸阳极氧化工艺使2060铝锂合金的抗拉强度和屈服强度下降了至少9％,在应力比0.06、应力水平240 MPa之下的中值疲劳寿命降低了90％.%Anodic oxidation coatings were prepared on 2060 Al–Li alloy in boric–sulfuric acid(45.0 g/L H2SO4+8.0 g/L H3BO3),sulfuric acid(160.0 g/L H2SO4),and mixed acid(140.0 g/L H2SO4+20.0 g/L H2C2O4·H2O+50.0 g/L NaKC4H4O6·4H2O+1.5 g/L additive),respectively.The effect of voltage or current on their properties were discussed.The thickness of anodic oxidation coating was measured by metallographic method,the micromorphology of the anodic oxidation coating was observed by scanning electron microscopy,and the mechanical properties of Al–Li alloy before and after anodization were tested by static stretching and tension–tension fatigue tests.The reason why anodization process influence the fatigue performance of Al–Li alloy was analyzed based on the morphology observation of fatigue fracture.Anodic oxidation coatings with uniform color and smooth surface can be formed in all three electrolytes.The thickness of anodic oxidation coating formed in boric–sulfuric acid is less than 2 μm,while that formed in sulfuric acid or mixed acid can reach 15 μm.The corrosion resistance of Al–Li alloy is greatly improved by anodization.The coatings formed in mixed acid,sulfuric acid,and boric–sulfuric acid endured 870 h,378 h,and 87 h respectively in neutral salt spray test,all of which are much longer than 8 h of the pure Al–Li alloy.However,the tensile strength and yield strength of 2060 Al–Li alloy were decreased by at least 9％and its median fatigue life was decreased by as much as 90％at a stress ratio of 0.06 and a stress level of 240 MPa after anodization in mixed acid.