研究了Zn含量(质量分数)分别为4.3%, 6%和8.6%的Mg-Zn-Y-Zr合金在5%(质量分数)NaCl溶液中的质量损失腐蚀和电化学腐蚀行为, 并对不同腐蚀时间的合金表面腐蚀形貌、微观组织和相成分进行了分析. 结果表明, Mg-Zn-Y-Zr合金中的第二相和Zn含量可显著影响合金的耐腐蚀性能, Zn含量为4.3%的Mg-Zn-Y-Zr合金表现出良好的抗腐蚀性能. 随着Zn含量的增加, 合金晶界上形成了电偶腐蚀加速效应更强的W相, 同时使α-Mg基体中的Zn含量增加, 从而导致合金的耐蚀性能逐渐变差.
In recent years, Mg-Zn-Y-Zr alloys have attracted significant interest due to the high strength at room and elevated temperature. Current researches mainly focus on the microstructures and mechanical properties of Mg-Zn-Y-Zr alloys, however, the corrosion behaviors of Mg-Zn-Y-Zr alloys have been seldom studied. In the present paper, the mass loss corrosion and electrochemical corrosion behavior of three Mg-Zn-Y-Zr alloys with Zn contents of 4.3% (mass fraction), 6% and 8.6% in 5% (mass fraction) NaCl solution were studied, respectively. The morphology, microstructure and phase composition of these alloys after different immersion time were observed. The results showed that the type of second phase and the content of Zn in these alloys significantly affect their corrosion resistance performance and the Mg-Zn-Y-Zr alloy with 4.3% Zn exhibited better corrosion resistance. With the increase of Zn content, the W phase with stronger effect of galvanic corrosion formed at grain boundaries and the content of Zn in α-Mg matrix also increased, which resulted in the worse corrosion performance. Experimental results also showed that the corrosion process of Mg-4.3Zn-0.7Y-0.6Zr alloy can be divided into three stages: galvanic corrosion, Zr-rich zone-Zr--poor zone corrosion and pitting corrosion.
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