(中南大學 材料科學與工程學院，長沙 410083)
摘 要: 基于原位腐蝕觀察方法，采用光學顯微鏡(OM)、掃描電鏡(SEM)和能譜分析(EDS)、鹽水浸泡實驗等研究Mg-Gd-Y-Nd-Zr合金在3.5%NaCl(質量分數(shù))溶液中的腐蝕機理，探討不同第二相在合金局部腐蝕中的作用機制。結果表明，合金腐蝕初期表現(xiàn)出典型的點蝕特征，富Gd和富Y粒子作為陰極相導致邊緣基體相α-Mg的優(yōu)先溶解，富Zr粒子中的Mg和邊緣α-Mg都優(yōu)先發(fā)生腐蝕，且腐蝕源的具體位置與第二相粒子和基體表面間的方位有關。在局部腐蝕過程中，具有更高稀土或鋯含量的第二相微區(qū)表現(xiàn)出更好的耐蝕性能。此外，在第二相密集分布的區(qū)域，第二相粒子充當腐蝕屏障，使微區(qū)的耐蝕性能提高。
關鍵字: 稀土鎂合金；第二相；鹽水浸泡；腐蝕
（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
