析出相对稀土镁合金腐蚀行为的影响-中国材料进展

文章信息/Info

Title:: Effect of Precipitates on Corrosion Behavior of Rare Earth Magnesium Alloys

Author(s):: KE Jing; GUO Lingtong; Xi ’an University of Architecture and Technology，School of Metallurgical Engineering, Xi ’an 710055, Shaanxi, P. R. China

Keywords:: Mg-Y-Sm-Zn-Zr magnesium alloy; precipitates; microstructure; corrosion behavior; corrosion film

摘要:: 镁合金由于密度低、比强度高、良好的电磁屏蔽性能而被广泛应用在航空航天、汽车、数码等重要领域，但其较差的腐蚀性能使进一步应用受到限制。稀土元素的晶体结构与镁合金相同，在α-Mg中具有较大的固溶度，形成的金属间化合物第二相可细化合金晶粒，同时加入稀土元素改变腐蚀结构，进而可以有效地改善镁合金的腐蚀性能。通过X射线荧光光谱仪、光学显微镜、扫描电子显微镜、电化学站测试、原子力显微镜等测试设备，表征了Mg-3.4Y-3.6Sm-2.6Zn-0.8Zr合金在3.5% NaCl溶液（质量分数）中的腐蚀速率和腐蚀形貌，研究了析出相对稀土镁合金腐蚀行为的影响。结果表明，稀土元素Y和Sm在镁合金中形成了(Mg,Zn)3(Y,Sm)和Mg12(Y,Sm)Zn 2种析出相，在合金腐蚀过程中(Mg,Zn)3(Y,Sm)相最先被腐蚀，随后是α-Mg基体和Mg12(Y,Sm)Zn相。析出相在合金腐蚀过程中形成了均匀的腐蚀产物膜层，增大了合金的电化学阻抗值，腐蚀产物膜层对合金起到了保护作用，有效地降低了合金的腐蚀速率。

Abstract:: Magnesium alloys are widely used in aerospace, automotive, digital and other important fields due to their low density, high specific strength, and good electromagnetic shielding properties, but their poor corrosion properties limit their applications. The crystol structure of rare earth elements is the same as that of magnesium alloys, and have a large solid solubility in α-Mg, the formed intermetallics second phase can refine grain size, and rare earth element can chage the microstructure fo corrosion layer, thus effectively improving the corrosion performance of magnesium alloys. In this paper, the corrosion rate and microstructure after corrosion of the Mg-3.4Y-3.6Sm-2.6Zn-0.8Zr alloy were characterized by X-ray fluorescence spectrometer, optical microscope, scanning electron microscope, electrochemical station, AFM test and other test equipments, and the influence of precipitation on the corrosion behavior of rare earth magnesium alloy was studied. The results show that rare earth elements Y and Sm form two precipitat (Mg,Zn)3(Y,Sm) and Mg12(Y,Sm)Zn in magnesium alloys. During the corrosion process，the (Mg,Zn)3(Y,Sm) phase is etched first, followed by the α-Mg matrix and the Mg12(Y,Sm)Zn phase. The precipitates form a corrosion product film during the alloy corrosion process, which increases the electrochemical impedance spectrum resistance value of the alloy. The corrosion product film protects the alloy and effectively reduces the corrosion rate.