Synergistic effects of wear and corrosion for Al 2 O 3 particulate-reinforced 6061 aluminum matrix composites
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INTRODUCTION
BECAUSE of the demands for high specific strength (strength-to-weight ratio) and specific stiffness, good high temperature capabilities and wear resistance in many engineering applications, metal-matrix composites (MMCs) have engendered extensive interest from industrial and academic researchers. The manufacturing processes of fiber-, whisker-, and particulate-reinforced MMCs have been well developed.[1] Because of the reduction in fabrication cost, the applications of MMCs have been widely extended to light weight bearing sleeves, calipers, automobile parts (brake rotors, drive shafts, connecting rods, piston rings, and cylinder liners), sporting goods, aerospace components, tanks (wheels, speed brakes, and track shoes), and other industrial applications. Among the three types of MMCs, particulate-reinforced MMCs are promising because of their isotropic material properties and low cost; additionally, they can be formed using conventional metal processing techniques. It is well known that wear resistance is significantly improved if the proper amount of reinforcement particles is added to the matrix.[2,3] However, the corrosion of the matrix can be increased due to the incorporation of reinforcements. Lore and Wolf[4] investigated the corrosion of SiC-reinforced 2024, 6061, and 7075 aluminum alloy– based MMCs. They found that the increase in corrosion due to the reinforcement phase was the most significant for 6061 Al matrix compared to the other matrices. The corrosion behavior of Al-based MMCs has been extensively C.-K. FANG, Associate Professor, is with the Department of Mechanical Engineering, China Institute of Technology and Commerce, Taipei, Taiwan 11522, Republic of China. C.C. HUANG, Process Engineer, is with the Taiwan Semiconductor Manufacturing Company Ltd., Hsin-Chu, Taiwan, Republic of China. T.H. CHUANG, Professor, is with the Institute of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan 106, Republic of China. Manuscript submitted May 19, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS A
studied.[5–11] 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. Clustered areas of particles may also enhance corrosion attack.[13] For alumina fiber–reinforced aluminum MMCs, no evidence of galvanic corrosion between Al2O3 and aluminum was reported,[12] while interfacial corrosion was observed. The preceding articles concentrated mainly on fiber-, whisker-, or SiCp-reinforced MMCs, while research on the corrosion behavior of alumina particulate–reinforced MMCs was rather limited. Although wear properties and corrosion behavior have been widely studied for engineering materials, published li
