稀土Sm对AZ92镁合金耐腐蚀性能的影响

Effect of Samarium on Corrosion Behavior of As-Cast AZ92 Magnesium Alloy

以AZ92镁合金为研究对象,添加少量稀土Sm(0～1.1%),利用扫描电子显微镜、X射线能谱分析法、静态腐蚀失重法和电化学测试等方法研究了少量稀土Sm对AZ92镁合金微观组织、腐蚀速率影响,并探讨了稀土Sm对AZ92镁合金耐腐蚀性能的影响机制。结果表明:随着合金中Sm含量的增加,AZ92合金中粗大枝状β-Mg17Al12组织枝晶断裂,逐渐转变为小岛状,体积分数下降,同时Sm原子结合Al,Mn原子转变成颗粒状Al-Mn-Sm相和Al-Sm相;通过静态腐蚀失重和电化学实验可知AZ92-xSm合金抗腐蚀性能优于AZ92合金。在3.5%NaCl水溶液中,Sm含量达到0.5%时,镁合金腐蚀速率趋于最小值,仅为AZ92合金的42%左右,抗腐蚀性能明显提高。

This paper focused on AZ92 magnesium alloys prepared by a simple addition of samarium （0 - 1.1% ）. The microstruc- ture, corrosion rate of as-cast AZ92-xSm alloys were characterized by using microscope, scanning electron microscopy, X-ray analysis, immersion tests, potentiodynamic polarization, electrochemical impedance spectroscopy （EIS）, and the mechanism of improving corro- sion behavior caused by samarium was also discussed. The results showed that increasing amount of Sm, the dendritic arm of coarse dendritic β-Mg17 Al12 disappeared, and gradually changed into slender island, and the volume fraction of 13 decreased, in addition, Sm atom combined with A1, Mn atoms formed particles of A1-Mn-Sm phase and A1-Sm phase; proper amount of Sm in the alloys could form small particles of A1-Mn-Sm phase and A1-Mn phase ; according to static corrosion test and electrochemical test, Sm could improve the corrosion resistance of AZ92 alloy. In 3.5% NaC1 solution, the corrosion rate of AZ92 alloy with 0.5% Sm was slight, and the corro- sion resistance was improved effectively, merely divided to 42% of AZ92 alloy.