Er对7075铝合金微弧氧化层特性的影响

对含Er量为0%、0.2%、0.4%的7075铝合金在相同工艺下进行微弧氧化,利用X射线衍射(XRD)、扫描电子显微镜(SEM)分别研究了微弧氧化膜层的相组成和表面形貌,同时也研究了氧化层的显微硬度、厚度及耐蚀性。结果表明,不同Er含量的7075铝合金微弧氧化层都由γ-Al_2O_3相构成,且随含Er量增加,γ-Al_2O_3相峰值增加,Er在微弧氧化过程中形成了Al_(17)Er_2相进入膜层;随含Er量的增加,氧化膜表面平整度先增加后下降,当Er含量为0.2%时,表面堆积物细小均匀、孔隙直径小,粗糙度最低;含Er量由0%增加到0.4%,显微硬度及厚度也随之增加,耐蚀性明显增加,自腐蚀电流密度由4.280×10~(-6) A/cm~2降至2.405×10~(-9) A/cm~2。

Effect of Er on characteristics of oxide coating on 7075 aluminum alloy by micro-arc oxidation

The 7075 aluminum alloys with 0%, 0.2% and 0.4% Er were subjected to micro-arc oxidation under the same parameters. The surface morphology and the phases of the oxide coating were analyzed using SEM and XRD. The micro-hardness, thickness and corrosion resistance of the oxide coating were also studied. The results show that the micro-arc oxidation coating of 7075 aluminum alloy with different Er contents is composed of gamma- Al2O3 phase. With the increase of Er content, the peak of gamma- Al2O3 phase is enhanced. Er enters the oxide coating with the form of Al17Er2, which is an unbalanced phase after micro-arc action. With the increase of Er content, the surface roughness of oxide coating decreases firstly and then increases. When Er content is 0.2%, the surface deposit is fine and uniform, the diameter of pore is small, and the roughness is the lowest. As the Er content increases from 0% to 0.4%, the micro-hardness and thickness of the oxide coating also increases, and then the corrosion resistance increases significantly. Consequently, the self-corrosion current density decreases from 4.280×10^-6A/cm² to 2.405×10^-9A/cm².