Corrosion Behavior of SiCp/6061 Al Metal Matrix Composites

Abstract

The corrosion behavior of silicon carbide/aluminum (SiCp/ Al) metal matrix composites was studied in chloride solution by means of electrochemical techniques, scanning electron microscopy (SEM), Auger electron spectroscopy (AES), energy dispersive spectroscopy (EDS), and X-ray diffraction. The materials under investigation were powder metallurgy (PIM) processed 6061 Al reinforced with increasing amounts of SiC particles (15 to 40 vol%). Electrochemical tests such as potentiodynamic polarization were done in 0.035, 0.35, and 3.5% NaCI solutions that were open to air, aerated, or deaerated to observe overall corrosion behavior. In addition, pit morphology was observed after anodic polarization to a number of potentials. It was seen that the corrosion potentials did not vary greatly or show definite trends in relation to the amounts of SiCp reinforcement. However, the degree of corrosion increased with increasing SiCp content and the presence or absence of oxygen as well as the concentration of the NaCI solution did affect corrosion potentials. Microscopic analysis techniques were used to study the corroded samples and the extensive pitting and exfoliation of the surfaces. X-ray diffraction was used to identify the compounds on the surface of the corroded samples as well as the flakes due to exfoliation.

Synergistic effects of wear and corrosion for Al2O3 particulate-reinforced 6061 aluminum matrix composites

“…The MMC with a higher volume fraction of reinforcement results in a more active corrosion potential and a higher passive current density. Similar results for corrosion potential were observed in Sun et al [9] study of SiC p /Al MMCs in open-to-air tests in 3.5 pct NaCl solution, a consequence of localized corrosion occuring at the reinforcement/matrix interface. Pre-existing defects due to incomplete interfacial cohesion between the matrix and reinforcement allowed easier achievement of the local chemistry required to retard repassivation and enhance localized attack.…”

“…The corrosion behavior of Al-based MMCs has been extensively C studied. [5][6][7][8][9][10][11] A review of corrosion studies on aluminum MMCs based on silicon carbide, graphite, alumina, and boron reinforcements can be found in Turnbull's [12] review article. In general, the reinforcement may introduce imperfections in the surface oxide on the matrix surface, and preferential attack occurs due to galvanic couples, active reaction products, intermetallic particles, microvoids, and microcrevices at reinforcement/matrix interfaces.…”

Corrosion behaviour of aluminium metal matrix composites reinforced with TiC processed by pressureless melt infiltration

“…The interfaces were preferred sites for passive film breakdown (pitting initiation sites), that produce voids, resulting in an easier breakdown of the oxide layer [7][8][9]. Pitting in composites has been observed at the reinforcement matrix interface [10][11][12]. Factors influencing the corrosion of composites include porosity, precipitation of intermetallic phases within the matrix, high dislocation densities at the particle-matrix interfaces, the presence of an interfacial reaction product and electrical conductivity of the reinforcements.…”

Metal–Matrix Composites

“…Experimental results have generally indicated that the corrosion rate of particulate and whisker Al/SiC MMCs are higher than the monolithic matrix alloy [81][82][83][84] and increase with SiC content [84,85] in aerated, chloride-containing environments. Weight loss data of 6092/SiC/P-T6 Al MMCs showed an increase in the corrosion rate as the SiC content increased from 5, 10, 20, 40, to 50 vol % for various 90-day humidity chamber tests [86].…”