反应时间对AZ31镁合金化学转化膜形貌和性能的影响

Effect of Different Reaction Time on Chemical Film-forming Micro Morphology on AZ31 Magnesium Alloy

采用化学成膜方法,以磷酸盐为化学转化液主要成分在一定工艺条件下对AZ31镁合金进行不同反应时间的表面处理,采用CASS盐雾腐蚀试验检测基体及膜层耐蚀性,采用划格试验测试膜基结合力。利用SEM、莱卡高级金相显微镜以及膜层测厚仪、粗糙度仪等对所制备出的膜层进行微观形貌观察、厚度与粗糙度的测试与分析。结果表明:化学转化膜表面呈现胞状形态特征,随着反应时间的延长,膜层的形貌变化规律为薄层、不连续→连续、均匀致密、无表面缺陷→生成网状裂纹→裂纹明显增粗;随着反应时间的延长,膜层厚度从2.45μm增大到4.68μm,但增大趋势逐渐放缓;膜层粗糙度随反应时间的增加变化不大;膜层耐蚀性均好于基体,反应时间为15s时膜层的耐蚀性最好;膜层与基体间结合力良好。

AZ31 magnesium alloy was treated by chemical film-forming method with phosphate as the main component of chemical conversion solution under certain process conditions for different reaction times.The corrosion resistance of substrate and film was tested by CASS salt spray corrosion test,and the bonding force of film substrate was tested by cross cut test.SEM,Leica advanced metallographic microscope,film thickness meter and roughness meter were used to observe the micro morphology,test and analyze the thickness and roughness of the prepared film.The results show that the surface of the chemical conversion film presents cellular morphological characteristics.With the extension of reaction time,the morphological change law of the film is thin layer, discontinuous → continuous, uniform and dense, no surface defects → Network Cracks → cracks increase obviously;With the extension of reaction time, the film thickness increased from 2.45 μ M increased to 4.68 μ m. But the increasing trend gradually slowed down;The film roughness changed little with the increase of reaction time;The corrosion resistance of the film is better than that of the substrate, and the corrosion resistance of the film is the best when the reaction time is 15s;The adhesion between the film and the substrate is good.