含稀土耐蚀Mg-9Al铸造镁合金腐蚀行为研究

CORROSION BEHAVIOR OF DIE-CAST Mg-9Al MAGNESIUM ALLOY WITH RE ADDITION

通过盐雾、失重及析氢等腐蚀试验研究了新研制的含稀土的Mg-9Al铸造镁合金AR091在3.5%NaCl溶液中的腐蚀行为,并与目前常用的ZM5和AZ91D镁合金的腐蚀行为进行了对比。结果表明,AR091具有良好的耐腐蚀性能。AR091的微观组织与AZ91有明显差别,其晶粒更为细小,β相明显减少,还存在许多针状含稀土元素(RE)的析出相。合金内各相间的微电偶腐蚀明显减弱,阴极反应过程受到抑制。采用场发射扫描电镜(FESEM)及俄歇电子谱(AES)研究比较了合金的表面腐蚀产物膜,结果表明,在AR091合金表面能形成更为致密、保护性更好的腐蚀产物膜。

The corrosion behavior of die-cast Mg-9Al magnesium alloy with RE addition （AR091） has been evaluated by general corrosion measurements and electrochemical methods in 3. 5N NaCl solution saturated with Mg（OH）2. The experimental results were compared with those of commercial magnesium alloy ZM5 and AZ91D. AR091 magnesium alloy has better corrosion resistance than ZM5 and AZg1D alloy. The microstructure of AR091, ZM5 and AZ91D were examined by Electron Probe Microanalysis （EPMA） and Energy Dispersion Spectroscopy （EDS）. The AR091 magnesium alloy showed microstructure characterized by a-phase solid solution, surrounded by less β-phase and more needle-like RE-containing phase. The excellent corrosion resistance of the AR091 alloy could be explained by the fact that the precipitated RE-containing phases are less cathodic. Moreover, the corrosion product film formed on the AR091 alloy surface was more protective.