正向电压对镁合金微弧氧化膜层相结构的影响

Effect of Positive Voltage on Phase Structure of Micro-arc Oxidation Films of Magnesium Alloy

摘要:

采用微弧氧化技术，以30 g/L的磷酸钠为电解液，利用系统的XRD手段研究了正向电压对AZ31镁合金表面微弧氧化膜层不同厚度的相组成，计算出晶粒尺寸、晶面间距和残余应力的分布规律。结果表明：电压不同膜层中各深度相的衍射峰强度、相组成和结晶度都不同，其中Mg3(PO4)2 (200)峰的晶粒尺寸随电压增加而变粗，且同一电压制备的膜层在同一晶向不同厚度的晶粒尺寸不一样，其值呈至膜层表面距离减小而减小，晶面间距也呈减小趋势；MgO相组成的涂层残余应力处于拉应力，其值随电压增加而显著减小。

Abstract:

The composite coatings on AZ31 magnesium alloy substrate were prepared by micro-arc oxidation (MAO) technique in sodium phosphate electrolyte. The effects of positive voltage on phase composition of different-thickness MAO films were investigated. Grain size, d-spacing and residual stresses were calculated based on systematical XRD class study. Results reveal that the diffraction peak intensity, phases and crystallinity of different-depth are different and the grain size of Mg3(PO4)2 (200) peak becomes bigger with increasing the positive voltage. Even preparing the film under the same voltage, the grain sizes of the same crystal orientation at different depths are still different, decreasing with reducing the depth from the surface of thin films, while the d-spacing has the same tendency. Residual stresses attributed to the MgO constituent of the coatings were calculated to be tensile. With the increase of the applied voltages, stress values are decreased sharply.