The effect of participate reinforcement on the sliding wear behavior of aluminum matrix composites
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INTRODUCTION
M E T A L matrix, particulate composites (MMCs) are well known for their higher specific modulus and strength when compared to conventional alloys It'2'31 and, more recently, for their excellent wear resistance. 14,51As a result, MMCs are fast becoming a cost-effective alternative to conventional materials in a number of specialized application areas. 16'71 A reasonable amount of data exists in the literature on the tribological behavior of particulate MMCs based on aluminum alloys. Sato and Mehrabian I8] have characterized the wear and friction characteristics of an A1-4Cu0.75Mg alloy reinforced with a wide range of particles (alumina, SiC, TiC, silica, and silicon nitride). These wear tests (pin on disc; 52100 bearing steel disc) indicated that the wear rates of particulate composites were lower than that of aluminum alloy by a factor of about 4, while the coefficients of friction of the composites were higher. A more detailed investigation by Hosking e t al. I9~ has demonstrated an increase in wear resistance with increasing volume fraction of alumina particulates (at constant particle size) and also with increasing particle size (at constant volume fraction). The coefficients of friction of the composites, however, were lower than that of the aluminum alloy without reinforcement. Surappa et al. tt~ noted an improvement in the wear resistance of AI and A1-Si alloys when reinforced with 5 wt pct alumina (100-/xm size). Similarly, Anand and Kishore t~tl observed a continuous decrease in wear rate with increasing corundum content (up to 30 wt pct) in an A1-Zn alloy. In an Al-l.5 Mg alloy, Rana and Stefanescu tl2J found a substantial decrease in the coefficient of friction with increasing volume fraction of SiC particulates. However, increasing the size of the SiC
MANISH ROY, B. VENKATARAMAN, V.V. BHANUPRASAD, Y.R. MAHAJAN, and G. SUNDARARAJAN, Scientists, are with the Defence Metallurgical Research Laboratory, Hyderabad-500 258, India. Manuscript submitted December 10, 1991. METALLURGICAL TRANSACTIONS A
particles from 50 to 100/zm at a constant volume fraction had a marginal effect on the coefficient of friction. Zam Zam tt3j has characterized the wear resistance of aluminum matrix composites containing up to 40 vol pct of - 5 0 /zm SiC. This work indicated that if SiC was well bonded to the matrix (achieved by hot pressing), the composite wear resistance increased continuously with increasing volume fraction of SiC. In contrast, if SiC was not well bonded to the matrix (as in the case of warm extrusion), the wear resistance of the composite increased up to a critical volume fraction of SiC and thereafter started to decrease. This critical volume fraction was observed to be dependent on the load applied during the wear test. The sliding wear behavior of an aluminum (2014)-SIC particle reinforced composite has been studied by Alpas and Embury tl41 using the block-on-ring type apparatus (hardened steel ring). This study indicated that the addition of 20 wt pct of 14-/xm size SiC particles to the 2
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