【摘要】 在硅酸盐溶液中于AZ31镁合金搅拌摩擦焊接头表面制备一层均匀的微弧氧化膜。分析微弧氧化膜的截面组织、相组成和显微硬度分布,并采用浸泡和电化学方法评估微弧氧化表面处理对焊接接头腐蚀行为的影响。结果表明:接头搅拌区的显微硬度高于镁合金母相区,热影响区硬度低于母相区,但接头不同区域对应的微弧氧化膜硬度都相同,比镁合金基体提高约7倍。在3.5%NaCl溶液中浸泡后,焊接样品热影响区腐蚀严重,而微弧氧化膜表面形貌没有明显变化。未表面处理的接头热影响区电位低于搅拌区和母相区,其腐蚀电流密度也较大,但不同区域微弧氧化膜的腐蚀电流密度都相近,并明显低于未氧化处理的焊接样品。微弧氧化表面处理能显著改善镁合金搅拌摩擦焊接头抗腐蚀性能。更多还原

【Abstract】 A uniform ceramic coating on friction stir welding(FSW) joint of AZ31 magnesium alloy was fabricated by microarc oxidation(MAO) in silicate electrolyte.Microstructure,phase constituent and microhardness profile of the MAO coating at the different zones of FSW joint were analyzed.The influence of microarc oxidation surface treatment on corrosion behaviors of FSW joint was evaluated by immersion and potentiodynamic polarization tests.The results show that hardness of stir zone is higher than that of base alloy,but the hardness of heat-affected zone is lower than that of base alloy.However,the microhardness of MAO coating at different zones of FSW joint is the same,which is about seven times higher than that of AZ31 base alloy.After immersion test in 3.5%NaCl(mass fraction) solution,the serious pitting corrosion on heat-affected zone takes place,but no pitting corrosion is observed on the MAO coating surface.In addition,the heat-affected zone of FSW joint has a lower corrosion potential and higher corrosion current density,but the corrosion current density of MAO coating at different zones is very close,which is much lower than that of bare AZ31 magnesium alloy.So the MAO surface treatment can significantly improve the corrosion resistance of FSW joint of AZ31 magnesium alloy.更多还原