第二相粒子在Mg-Gd-Y-Nd-Zr合金局部腐蚀中的作用机制

刘  俊，陈明安，马聪聪，黄宇迪，张新明，邓运来

(中南大学 材料科学与工程学院，长沙 410083)

摘 要：基于原位腐蚀观察方法，采用光学显微镜(OM)、扫描电镜(SEM)和能谱分析(EDS)、盐水浸泡实验等研究Mg-Gd-Y-Nd-Zr合金在3.5%NaCl(质量分数)溶液中的腐蚀机理，探讨不同第二相在合金局部腐蚀中的作用机制。结果表明，合金腐蚀初期表现出典型的点蚀特征，富Gd和富Y粒子作为阴极相导致边缘基体相α-Mg的优先溶解，富Zr粒子中的Mg和边缘α-Mg都优先发生腐蚀，且腐蚀源的具体位置与第二相粒子和基体表面间的方位有关。在局部腐蚀过程中，具有更高稀土或锆含量的第二相微区表现出更好的耐蚀性能。此外，在第二相密集分布的区域，第二相粒子充当腐蚀屏障，使微区的耐蚀性能提高。

关键词：稀土镁合金；第二相；盐水浸泡；腐蚀

Effect of second phase particles on localized corrosion of Mg-Gd-Y-Nd-Zr alloy

LIU Jun, CHEN Ming-an, MA Cong-cong, HUANG Yu-di, ZHANG Xin-ming, DENG Yun-lai

(School of Materials Science and Engineering, Central South University, Changsha 410083, China)

Abstract:Based on in-situ corrosion observation, the corrosion mechanism of Mg-Gd-Y-Nd-Zr alloy in 3.5% NaCl (mass fraction) solution was investigated by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS) and saline immersion test. The action mechanism of various second phase particles on localized corrosion of the alloy was also studied. The results show that pitting is the typical and obvious feature in the initial stage of corrosion. Gd-rich and Y-rich particles promote corrosion of α-Mg as cathode of corrosion galvanic cell, while both Mg in Zr-rich particle and α-Mg close to Zr-rich phase corrode preferentially. Moreover, the exact location of corrosion is concerned with the orientation between the second phase particle and the matrix. In the process of localized corrosion, the second phase with higher content of RE elements or Zr shows better corrosion resistance. Furthermore, the area distributed with intensive second phase particles exhibits better corrosion resistance, which is ascribed to the barrier effect derived from the interaction between particles.

Key words:rare earth magnesium alloy; second phase; saline immersion; corrosion