Ce含量对AZ31镁合金显微组织及耐蚀性能的影响

Influence of Cerium on Microstructure and Corrosion Resistance of AZ31 Magnesium Alloy

采用金相显微镜、X射线衍射仪、扫描电镜和失重腐蚀试验,研究了不同Ce加入量时AZ31镁合金的显微组织、相组成及其在3.5%NaCl溶液中浸泡后的表面腐蚀形貌及腐蚀速率。结果表明:AZ31镁合金的显微组织主要由α-Mg固溶体和β-Mg_(17)Al_(12)相组成;加入质量分数为1.0%Ce^3.5%Ce后,AZ31镁合金的组织主要为α-Mg固溶体和Al-Ce相。当Ce含量为1.0%时,Al-Ce相尺寸小、数量少且沿晶界分布;随Ce含量增加,Al-Ce相数量增加,且出现偏聚加重现象。当Ce含量≤1.4%时,随Ce含量的增加,AZ31镁合金浸泡腐蚀76 h后的失重腐蚀速率变化较小;但当Ce含量>1.4%时,随Ce含量增加,该合金腐蚀速率急剧增大,耐腐蚀性能下降。向AZ31镁合金中加入Ce,形成了Al-Ce相,抑制了β-Mg_(17)Al_(12)析出。添加1.0%Ce时,AZ31镁合金耐腐蚀性能达到最佳。

The microstructure and phase composition of AZ31 magnesium alloy with different Ce contents and its corrosion morphology and corrosion rate in 3.5% NaC1 solution were investigated by optical microscope, X-ray diffxactometer, scanning electron microscope and mass loss corrosion test. The results show that the microstructure of AZ31 magnesium alloy mainly consists of α-Mg solution and β-Mg17A112 phase. Adding 1.0wt%-3.5wt%Ce to AZ31 magnesium alloys, the microstructure of the alloy is mainly α-Mg solution and Al-Ce phase. When Ce content is 1.0%, a small amount of fine Al-Ce phases distribute at the grain boundaries. The amount of Al-Ce phases grow with Ce content increasing and much more severe segregation of Al-Ce phases appears. When Ce content is less than or equal to 1.4%, with the increase of Ce content, the corrosion rate of AZ31 magnesium alloy in 3.5%NaC1 solution for 76 h changes slightly. When the content of Ce is higher than 1.4%, with the increase of Ce content, the corrosion rate of AZ31 magnesium alloy increases dramatically, and the corrosion resistance decreases sharply. Adding Ce to AZ31 magnesium alloy, Al-Ce phase forms in the alloy, which can inhibit the precipitation of β-Mg17Al12. The optimal corrosion resistance of the alloy can be obtained when 1.0%Ce is added to the alloy.