Effect of Reinforcements on the Corrosion Behavior of SiCp/AA2124 Metal Matrix Composites

In the present study, two composites, reinforced with 25 vol% SiC particles with average sizes of 3 mu m (micrometer-sized, composite A) and 0.7 mu m (submicrometer-sized, composite B), respectively, were evaluated to investigate the effect of reinforcements on the corrosion behavior of SiCp/Al Alloy 2124 (UNS A92124) metal matrix composites. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements performed in a 0.6 M NaCl solution revealed that composite B, whose corrosion resistance was close to that of AA2124, exhibited higher corrosion resistance than composite A. It was found that the composition and distribution of the intermetallic particles in the aluminum matrix were altered by the addition of SiC particles. Preferential precipitation of Al2Cu (theta-phase) and Mg segregation in the SiC/Al interfacial regions were observed and are believed to be responsible for the inferior corrosion performance of composite A. The improved corrosion resistance of composite B was attributed to the decrease of the theta-phase precipitation in the SiC/Al interfacial regions and the reduced porosity, reducing the active sites for corrosion initiation.