AZ91D镁合金磷酸盐化学转化膜的组织及性能

Microstructure and Properties of Phosphate Chemical Conversion Coating on AZ91D Magnesium Alloy

采用镁合金磷酸盐化学转化工艺,利用扫描电镜(SEM)、X射线衍射(XRD)对膜的形貌、厚度以及相组成进行研究,利用盐雾和湿热试验箱检验基体以及化学转化膜的抗腐蚀性能,同时对AZ91D镁合金磷酸盐转化膜的成膜机理进行了初步探讨。结果表明,磷酸盐转化膜为显微网状结构,存在一些显微裂纹,膜厚为7.6μm,成膜比较均匀,对基体有较好的覆盖作用,膜层由一些无定形相组成,膜的组分主要含有P、O、Al、Ba、F、Mg元素,经盐雾和湿热检测,磷酸盐转化膜可以有效地提高AZ91D镁合金基体的防腐性能。

Morphology,thickness and phase constituent of phosphate chemical conversion coating on the die casting AZ91D magnesium alloy were investigated by SEM(scanning electron microscope)and XRD(X-ray diffraction),and the corrosion resistance of the coating and the matrix alloy were examined in salt spray and damp testing.In addition,the formation mechanism of the coating was described.The results indicate that the phosphate chemical conversion coating exhibits micro-net like structure with some micro-crack and 7.6 μm in thickness as well as uniform distribution,showing excellent protection for the matrix alloy.The coating is composed of amorphous phase,and the chemical compositions in the coating mainly include P,O,Al,Ba,F,Mg elements.The salt spray and damp testing verify that the coating can distinctly improve the corrosion resistance of the AZ91D magnesium alloy matrix.