Wear of al-based hybrid composites containing BN and SiC particulates
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Wear of Al-Based Hybrid Composites Containing BN and SiC Particulates S.C. TJONG, K.C. LAU, and S.Q. WU During the last decade, aluminum alloys discontinuously reinforced with ceramic particulates have received increasing attention for various high-performance applications in automotive, aerospace, and transportation industries due to their high strength-to-weight ratio and superior wear resistance. For example, particulate-reinforced metal matrix composites (MMCs) can be used as structural materials for the pistons and connecting rods of automotive engines. Furthermore, particulate-reinforced MMCs also offer several advantages compared to the continuous fiber-reinforced composite such as improved anisotropy, ease of fabrication, and low cost. Particulate-reinforced MMCs can be produced by ingot metallurgy (IM) and powder metallurgy (PM) processing routes. The advantages of PM over IM processing in the fabrication of MMCs include near-net-shape fabrication, lower processing temperatures, and improved microstructural homogeneity. Several hard ceramic particles like SiC, Al2O3, TiC and TiB2 have been introduced into aluminum alloy matrices to increase their mechanical and wear properties. Among these, the wear behavior of SiC particulatereinforced MMCs has been investigated extensively by several researchers.[1–10] Generally, the wear resistance of MMCs increases with increasing volume fractions and sizes of the SiC particulates. However, the wear mechanisms of these MMCs remain unclear owing to the complications created by the ceramic particles. More recently, Tandon and co-workers have reported that during dry sliding wear of SiC-reinforced Al-Si composites, an amorphous surface mixed layer (SML) composed of heavily deformed matrix
S.C. TJONG, Associate Professor, and K.C. LAU, Graduate Student, are with the Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong. S.Q. WU, Professor, is with the Department of Materials Science and Engineering, Southeast University, Nanjing, 210096, P.R. China. Manuscript submitted October 27, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS A
and fragmented SiC particles is formed at the mating interface of MMCs. The depth of SML depends on the applied load and sliding distance. The SML has a large influence on the wear rates of MMCs as the wear debris mainly comes from the SML.[4,5] Compared to the vast number of studies on conventional discontinuously reinforced MMCs, limited effort has been directed toward composites containing different kinds of ceramic reinforcements in the form of particulates, fibers, or whiskers. The broad variety of ceramic reinforcements with unique properties allows one to design the hybrid composites with superior wear resistance. Recently, Song et al. have prepared Al composites reinforced with carbon and Al2O3 fibers by means of the squeeze-casting techniques. They reported that the wear resistance of C 1 Al2O3/Al hybrid composites is remarkably higher than that in the Al2O3/Al MMC specimens.[11] Gurcan and Baker
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