SiC_p／Al复合材料的界面优先溶解

THE INTERFACIAL PREFERENTIAL DISSOLUTION ON SiC_p/Al COMPOSITES

本文报导了ＳｉＣｐ／Ａｌ复合材料在ＮａＣｌ水溶液中的增强体／基体界面优先溶解（ＩＰＤ）现象．计算了淬火时形成的界面附近基体的塑性变形区尺寸．理论分析表明ＩＰＤ系由界面塑性区加速溶解引起．考察了ＩＰＤ在复合材料腐蚀中的作用，发现ＩＰＤ能使高ＳｉＣ含量材料均匀溶解，并能抑制点蚀．

ccording to the previous researches on corrosion of discontinuously reinforced Al alloy matrix composite, the role of reinforcement / matrix interface in corrosion is nothing but a preferable site for pitting initiation. The interfacial preferential dissolution (IPD) on SiCp/ Al composites as immersed in NaCl solution is reported in this article. IPD is not pitting at all for the operating mechanism is quite different from that for pitting, i.e. the occluded cell. IPD occurs on the composites with either pure Al or LY12 Al alloy matrix, no matter whether they are fabricated by cast or powder metallurgy process. Width of the plastically deformed zone around the interface, formed in quenching, resulting from the difference in coefficients of thermal expansion between reinforcement and matrix, is deduced to be 0.5D, where D is the diameter of SiC particulate. It is in coincidence with IPD's width, measured 0.3-0.4D. It is concluded that IPD is due to the poor integtity of the surface oxide film upon the plastic zone, independent the of chemical, metallurgical and galvanic-couple factors around the interface, if any. The copper-deposition test does indicate this poor integrity. The long term immersion test reveals that IPD causes intensified dissolution at SiC clusters and uniform dissolution for the composite with high SiC content. Moreover, IPD and pitting depress each other by cathodic protection. Most pits are located at the metallurgical imperfections.