Ca对Mg-11Gd-3Y-0.5Zr合金显微组织和耐蚀性的影响

Effect of Ca on microstructure and corrosion resistance of Mg-11Gd-3Y-0.5Zr alloy

采用静态质量损失法、电化学测试方法研究了加入不同含量的Ca(0 mass%,0.2 mass%,0.8 mass%)对时效态Mg-11Gd-3Y-0.5Zr合金耐腐蚀性能的影响,运用光学显微镜、扫描电镜和X射线衍射仪对合金的组织和物相以及腐蚀产物形貌和物相进行分析。结果表明:时效态Mg-11Gd-3Y-0.5Zr合金主要由α-Mg基体、Mg5Gd和Mg24Y5相组成,晶粒尺寸随着Ca含量的增加而减小,细化效果显著;当Ca含量为0.2 mass%时,其主要以固溶的形式存在,合金相的种类没有改变,但Ca含量为0.8 mass%时,合金有新相Mg2Ca的生成且晶界处的第二相明显增多。在本文研究范围内,Mg-11Gd-3Y-0.2Ca-0.5Zr合金自腐蚀电位最高,腐蚀电流密度最小,合金的耐蚀性最好;合金表面的腐蚀产物主要是由Mg(OH)2以及少量的Mg5Gd和Mg24Y5相组成。

The effect of different contents of Ca(0 mass%,0.2 mass%,0.8 mass%)on corrosion resistance of aged Mg-11 Gd-3 Y-0.5 Zr alloy was studied by means of static mass loss method and electrochemical test.The microstructure and phase of the alloy and the morphology and phase of corrosion products were analyzed by means of optical microscope,scanning electron microscopy and X-ray diffractometer.The results show that the aged Mg-11 Gd-3 Y-0.5 Zr alloy is mainly composed ofα-Mg matrix,Mg5Gd and Mg24Y5 phases.The grain size of the alloy decreases with the increase of Ca content,and the refining effect is significant.When the content of Ca is 0.2 mass%,the alloy exists mainly in the form of solid solution,and the phase type does not change,but when the content of Ca is 0.8 mass%,the new phase Mg2Ca is formed in the alloy,and the second phase at the grain boundary obviously increases.Within the scope of this study,the Mg-11 Gd-3 Y-0.2 Ca-0.5 Zr alloy has the highest self-corrosion potential,the lowest corrosion current density and the best corrosion resistance.The corrosion products on the alloy surface are mainly composed of Mg(OH)2 and a small amount of Mg5Gd and Mg24Y5 phases.