AZ91镁合金表面微弧氧化与磁控溅射镀铜复合处理层的微观组织与性能

Microstructure and Properties of Duplex Coating on AZ91 Magnesium Alloy Combined with MAO and Magnetic Sputtering Copper

摘要:

采用微弧氧化技术在AZ91镁合金表面制备陶瓷涂层，然后在该涂层表面通过磁控溅射镀铜技术制备复合膜层。研究了微弧氧化陶瓷层和复合膜层的表面物相组成、表面粗糙度、表面及截面形貌、表面润湿性及电化学性能。结果表明：AZ91镁合金经微弧氧化处理后由于微弧氧化陶瓷层呈微纳粗糙多孔结构，表现为亲水特性，其物相由MgO、Mg及Mg2SiO4组成；而微弧氧化陶瓷层经磁控溅射镀铜处理后表面获得较为致密的具有疏水特性的铜层，表面粗糙度降低；四探针测试结果说明复合膜层的方阻为16.2mΩ?□-1，导电性良好；动电位极化曲线测试结果说明复合膜层与基体镁合金相比，其腐蚀电流密度降低10%，腐蚀电位提高了0.36V，腐蚀极化电阻提高约80倍；与微弧氧化陶瓷层相比，复合膜层的腐蚀电位提高了0.24V，但其腐蚀电流密度和腐蚀极化电阻有所下降。研究结果表明，微弧氧化与磁控溅射镀铜相结合的复合处理技术可在不降低镁合金陶瓷层耐蚀性的基础上显著提高其表面的导电性能。

Abstract:

Porous ceramic coating were prepared on AZ91 magnesium alloy by micro-arc oxidation (MAO), and the duplex coating were prepared by magnetic sputtering copper. The surface phase?composition, surface roughness, surface and cross-sectional morphology, surface wettability, and electrochemical characteristics of MAO and duplex coatings were studied. The results indicate that the surface of AZ91 magnesium alloy treated by MAO shows hydrophilic due to its micro-nano coarse porous structure, and its phase?consists of MgO, Mg and Mg2SiO4. However, the surface of MAO coating turns into relatively compact copper with hydrophobic property after magnetic sputtering copper, at the same time the surface roughness decreases a little. Four-point probe measurement indicates that the duplex coating exhibits well electrical conductivity,the sheet resistance is 16.2mΩ?□-1. Meanwhile, potentiodynamic polarization curves reveal that the corrosion current density of duplex coating reduces to 10%, and the corrosion?potential increases 0.36V, while the polarization resistance increases around 80?times compared with bare magnesium alloy. Compared with the MAO coating, the corrosion?potential of the duplex coating increases 0.24V, suggesting that the corrosion trend decreases. Nevertheless, the corrosion current density and polarization resistance of the duplex coating all decrease to some extent. These?survey?results?indicate that the duplex treatment by MAO and magnetic sputtering copper on surface of the magnesium alloy improve its electrical conductivity greatly?without?losing corrosion resistance of magnesium alloy.