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Top1. Introduction
Metal Matrix Composites (MMCs) are being increasingly used in aerospace and automobile industries owing to their enhanced properties such as elastic modulus, hardness, tensile strength at room and elevated temperatures, wear resistance combined with significant weigh saving over unreinforced alloys. New fibers, new matrices, novel composite architectures and innovative manufacturing processes continue to provide exciting opportunities for improvements in performance and reductions in cost, which are essential to maintain competitiveness in increasingly globalized world markets. Predicting composite behavior continues to improve with enhanced scientific understanding and modeling capability, allowing much more effective and reliable use of these complex materials (Cantor et al., 2003). Composite materials offer superior combination of properties in such a manner that today no existing monolithic material can rival. Over the years, several types of composite materials have been used in numerous structural, non-structural and functional applications in different engineering sectors. Aluminum matrix composites (AMCs) refer to a class of light weight high performance aluminum centric material systems. The reinforcement in AMCs could be in the form of continuous/discontinuous fibers, whisker or particulates, in volume fractions ranging from different percentages. Properties of AMCs can be tailored to the demands of different industrial applications by suitable combinations of matrix, reinforcement and processing route (Surappa, 2003).
Wear is one of the most commonly encountered industrial problems, leading to frequent replacement of components, particularly abrasion. The particulate reinforcement such as Al2O3 and aluminide (Husking et al., 1982; Hutching, 1987) are generally preferred to impart higher hardness. Although there is no clear relation between mechanical properties of the composites, volume fraction, type of reinforcement and surface nature of reinforcements, the reduced size of the reinforcement particles is believed to be effective in improving the strength of the composites (Ma & Tjong, 1997). The structure and properties of the reinforcements control the mechanical properties of the composites. Further, the improved interface strength and better dispersion of the particles in the matrix can also be achieved by preheating the reinforcements (Chen et al., 1997; Thakur & Dhindaw, 2001). Kumar and Balasubramanian (2008) developed a mathematical model to evaluate wear rate of AA7075/SiCp powder metallurgy composites. The results showed that the volume fraction of reinforcement, sliding speed and applied load were varying directly proportional with wear rate, while particle size of reinforcement and hardness of counterpart materials were having inversely proportional with wear rate. Modi et al. (2001) showed that the effect of applied load on the wear rate of both zinc alloy and the 10 wt. % Al2O3 particle-reinforcement composite using statistical analyses of the measured wear rate at different operating conditions. The effect of applied load on the wear rate of the composite was found to be more severe.