SiC_p/2024Al铝基复合材料点蚀发生和发展的原位研究

IN SITU INVESTIGATION OF PITTING INITIATION AND PROPAGATION IN SiC_p /2024 Al METAL MATRIX C0MPOSITES

本文研究了碳化硅颗粒（SiCp）的体积分数和介质中的Cl-含量对于SiCp／2024al铝基复合材料腐蚀性能的影响.用扫描微参比电极测量系统首次显示和跟踪了复合材料点蚀发生及发展的微区动态行为.动电位循环极化法研究表明，SiCp／2024al复合材料比相应的纯铝基金属有较大的腐蚀敏感性.SiCp体积分数和介质中的Cl-含量的增加均引起复合材料的点蚀电位的显著负移.扫描微电极技术研究表明，表面钝化膜的局部破坏和微孔腐蚀可在远负于点蚀发生电位的开路电位下发生.SiCp的体积分数的增加引起复合材料活性中心的明显增加.点腐蚀主要发生在SiC／al基体界面和第二相夹杂物／al基体界面.

The corrosion characteristics of as-cast SiCp/ 2024 al composites in chloride (Cl-) media were investigated using scanning micro reference electrode technique,electrochemical analysis and scanning electron microscopy. The composites have less resistant to pit initiation than the corresponding aluminum alloy. The increase in volume fraction of SiCp reinforced phase resulted in a signiflcant decrease of pitting potential. In situ mapping of the active centers in composites revealed that local breakdown of passivity and micropitting corrosion could happen even at the open-circuit potentials, and the increase of volume fraction of SiC particles reinforced phase in the composites led t0 a significant increase of active centers on their surfaces. Pitting corrosion attack occured preferentially at the interfaces of SiC / al, and al2Cu or (Cu, Fe, Mn)al6 inclusions / al for the composites.