A7N01P-T4铝合金MIG焊焊接接头微弧氧化涂层的微观形貌和耐腐蚀性

Microstructure and Corrosion Resistance of Micro-Arc Oxidation Coatings on Metal Inertia Gas Welding Joint of A7N01P-T4 Aluminum Alloy

微弧氧化可提高金属及其合金的性能,但目前有关铝合金焊接接头微弧氧化的研究报道较少。采用微弧氧化技术在A7N01P-T4铝合金熔化极惰性气体保护(MIG)焊焊接接头上制备一层陶瓷涂层,研究接头微弧氧化涂层的微观结构以及接头试样微弧氧化前后的耐腐蚀性能。利用金相显微镜对接头的微观金相形貌进行观察,利用扫描电镜(SEM)、能谱仪(EDS )、X射线衍射仪(XRD)、Image-Pro Plus图像软件、sj-210便携式粗糙度仪对接头涂层的表面、截面微观形貌和结构进行分析,采用电化学工作站研究接头不同区域微弧氧化前后的耐腐蚀性能。结果表明:接头各区均由不同比例的a(Al)基体、粗大一次相和细小弥散二次相构成。接头各区涂层主要由A12O3构成,其含量差别较小。焊缝涂层厚度最大,热影响区涂层厚度最小。焊缝涂层孔隙率为17.4%,母材和热影响区涂层孔隙率分别为15.8%和15.7%。焊缝涂层粗糙度约为2.31μm,母材涂层和热影响区涂层粗糙度分别约为2.17μm和2.13 pm。电化学测试结果表明涂层明显提高了接头试样各区域的耐蚀性,焊缝涂层耐蚀性最好,热影响涂层耐蚀性最差,其中涂层致密层的厚度和缺陷是影响接头各区域耐蚀性高低的关键因素。

Ceramic coatings on the metal inertia gas (MIG) welding joint of A7N01P-T4 aluminum alloy were prepared by micro-arc oxidation (MAO) technology. The microscopic metallographic phase of the joint was observed by metallographic microscope. The surface morphology, cross-sectional morphology and microstructure were studied by means of SEM, EDS, XRD, image-pro Plus Image software, sj-210 portable roughness meter. The corrosion resistance of the joint before and after micro-arc oxidation in different areas was evaluated by electrochemical workstation. Results showed that each zone of the joint consisted of different proportions of a (Al) matrix, coarse primary phase and fine dispersed secondary phase. The coating of each zone of the joint was mainly composed of Al2O3, and the difference in content was small. The thickness of the weld zone was the maximum while that of the heat affected zone was the minimum. The porosity of the weld coating was 17.4%. The porosities of the base metal and heat affected zone were 15.8% and 15.7%, respectively. The roughness of the weld zone was about 2.31μm, and the roughness of the base metal and heat affected zone was about 2.17 pim and 2.13μm, respectively. Electrochemical test results showed that the coating obviously improved the corrosion resistance of the joint. The corrosion resistance of the weld coating was the best while the corrosion resistance of the heat-affected coating was the worst. The thickness and defects of the dense layer of the coating were the key factors affecting the corrosion resistance of each zone of the joint.