镁合金在含电解质水溶液中较差的耐腐蚀性能极大地限制了其工程应用。该文以开发一种有效改进镁合金耐蚀性能的加工工艺为目的，采用搅拌摩擦加工（friction stir processing，FSP）对铸态AZ91镁合金的耐蚀性进行改性处理，并分析了微观组织细化对镁合金耐蚀性的影响规律。通过电化学实验分析发现，加工处理后镁合金在质量分数3.5%的NaCl水溶液中的极化阻抗Rp提高了约1倍。微观组织分析结果表明是因为镁合金中的第二相β-Mg17Al12的形态和分布的改变影响了镁合金的腐蚀过程。一方面，细化的阴极相β-Mg17Al12增大了阳极与阴极的面积比，弱化了镁合金中严重的电偶腐蚀倾向。另一方面，大量细小的第二相β-Mg17Al12在腐蚀过程中再沉积在镁合金的表面形成保护层，显著抑制了α-Mg基体的腐蚀扩展。
Abstract
The poor corrosion resistance of magnesium alloys in aqueous solution containing electrolyte significantly restricts their engineering application. In this paper, with the aim of developing a new processing technique to efficiently improve the corrosion resistance of magnesium alloy, friction stir processing (FSP) was applied to modify the corrosion resistance of cast AZ91 magnesium alloy. And the effect of microstructural refinement on the corrosion resistance was investigated. The electrochemical measurements reveal that the polarization impendence Rp of processed alloy in NaCl solution with a mass fraction of 3.5% is nearly doubled. The results of microstructure analysis show that it is mainly attributed to the alteration of corrosion process induced by modification on the morphology and distribution of β-Mg17Al12 phase in magnesium alloys. On the one hand, the refinement of cathodic β-Mg17Al12 phase increases the area ratio of anode and cathode, which mitigates the severe galvanic corrosion in magnesium alloys. On the other hand, a large amount of fine β-Mg17Al12 particles could redeposit on the surface of magnesium alloy to form protective layer during corrosion and significantly inhibit the propagation of corrosion into α-Mg matrix.
关键词
腐蚀性能 /
AZ91D镁合金 /
搅拌摩擦加工(FSP) /
组织细化
Key words
corrosion behavior /
AZ91D magnesium alloys /
friction stir processing (FSP) /
microstructural refinement
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参考文献
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基金
国家自然科学基金资助项目（51375259）
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