Zn对Mg-RE-Mn合金组织和耐腐蚀性能的影响

Effect of Zn on Microstructures and Corrosion Resistance of Extruded Mg-RE-Mn Alloy

采用扫描电镜、XRD、电化学测试和化学浸泡试验,研究了Zn对挤压态Mg-RE-Mn镁合金显微组织以及在3.5%的NaCl溶液中耐腐蚀性能的影响。结果表明,加入Zn后,合金中有MgZn2、Mg2Zn11相生成,并显著细化了合金的晶粒。Zn能使合金的腐蚀电位正移,改善合金的耐腐蚀性能。当w(Zn)=1.5%时,合金晶粒细小,组织成分均匀,平均腐蚀速率仅为1.180mm/a。当w(Zn)=3.0%时,合金的析出相增多,并出现粗化、偏聚的趋势,以α-Mg为阳极,第二相(MgZn2等)为阴极的电偶腐蚀加剧,平均腐蚀速率为2.419mm/a。

Effects of Zn on microstructure of an extruded Mg-RE-Mn alloy and its corrosion behavior in 3.5%NaC1 solution were investigated by means of scanning electron microscope （SEM）, X-ray diffrac- tometer （XRD）, electrochemical test and chemical immersion methods. The results show that with Zn addition, secondary phase MgZn2. Mgz Znll are generated, and the grain size in the alloys is obviously re- fined. Zn can improve the anti-corrosion property of the alloy by shifting the pitting potential to a posi- tive value to some extent. With 1.5% Zn content, the grain size is decreased remarkably, and the micro- structure becomes homogeneous, meanwhile, the average corrosion rate of the alloy is only 1. 180 mm/a. When Zn content is 3.0%, the precipitates are increased with the trend of coarsening and segre- gation. So a galvanic corrosion which can be formed for the a-Mg as an anode and the second phase as a cathode accelerates the corrosion of the alloy, resulting in the average corrosion rate of the alloy of 2. 419 mm/a.