含钪Al-Zn-Cu-Mg-Zr合金的腐蚀行为和电化学阻抗谱特征

Corrosion behaviors and electrochemical impedance spectroscopy features of Al-Zn-Cu-Mg-Zr alloy containing Sc

通过晶间腐蚀、剥落腐蚀和极化曲线试验,结合电化学阻抗谱(EIS)测量,研究不同时效处理对含钪超高强Al-Zn-Cu-Mg-Zr合金的晶间腐蚀和剥落腐蚀敏感性的影响。研究结果表明:在自然时效状态下,合金腐蚀敏感性最大;人工时效处理的合金,其腐蚀敏感性随时效时间的延长而降低,相应时效态合金在EXCO溶液中恒电位极化曲线分析,也得出相同的结论。晶界析出相和晶界无沉淀析出带(PFZ)是影响合金腐蚀性能的主要因素。随着时效时间的延长,η′和S′相逐渐向平衡的η和S相转变,晶界析出相粗化并呈链状分布,PFZ变宽等均有助于降低合金的腐蚀敏感性。合金的电化学阻抗谱(EIS)演变对腐蚀类型的转变具有规律的反映,可以用来对合金的腐蚀性能进行快速、无损的检测。

The effects of various aging treatments on intergranular and exfoliation corrosion susceptibility of Al-Zn-Cu-Mg-Zr alloys containing Sc were studied using corrosion tests,polarization curve and electrochemical impedance spectroscopy（EIS）.The results show that the naturally aged（NA） alloy has the highest susceptibility of intergranular and exfoliation corrosion and the susceptibility of the alloys in artificial aging treatments decreases with the increase of aging time,which conforms to the relevant polarization test results of the alloys in EXCO solution.The analysis of transmission election microscopy（TEM） reveals that the precipitated phases on grain boundaries and the precipitation free zone（PFZ） influences the susceptibility of the alloys obviously.As the aging time prolongs,η′ and S′ phases transform into equilibrium η and S phases,and the discontinuous η and S phases and the coarsened PFZ at grain boundaries reduce the susceptibility of the alloys.The transformations of exfoliation corrosion are represented by EIS evolutions of the alloy which can be developed as a rapid and harmless test method of the corrosion susceptibility.