Characteristics of Mg-based composites synthesized using a novel mechanical disintegration and deposition technique
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INTRODUCTION THE ability of processing methodologies to influence the microstructurally governed properties of metallic materials has been instrumental in motivating materials scientists to modify and improve on existing techniques and to explore new processing routes. The success of a new processing methodology depends heavily on its industrial adaptability, cost effectiveness, and ability to produce materials with superior microstructure and properties with consistent reproducibility. For the synthesis of metallic-based materials, methods of processing can be classified into nonconventional methods such as the rapid solidification processing (RSP) technique and the commonly used conventional methods.[1,2,3] Conventional methods include liquid-phase processes,[1] two-phase processes[2] and solid-phase processes.[3] An example of each is casting, rheocasting, and powder metallurgy, respectively. For the synthesis of bulk materials, conventional methods are the preferred choice. Of these methods, liquid-phase processes are the most widely accepted processing techniques due to their low cost, high production rate,[1] and near net shape capability. Liquid-phase processes are also the preferred choice for the synthesis of metal matrix composites (MMCs). These materials have the ability to combine the properties of metals and the reinforcing phase to produce superior tailored mechanical, physical, and thermal properties. Potentially, they are a new class of materials for advanced structural, aerospace, automotive, electronic, thermal, wear, and sports applications.[4–9] The two main types of MMCs are continuously (fibers) reinforced and discontinuously (particulates) reinforced MMCs. Due to its high cost, fiber-reinforced MMCs are only used in specialized fields such as in aerospace and military operations. On the other hand, the most M.K.K. OO and P.S. LING, Graduate Students, and M. GUPTA, Associate Professor, are with the Department of Mechanical and Production Engineering, National University of Singapore, Singapore 119260. Manuscript submitted August 18, 1999. METALLURGICAL AND MATERIALS TRANSACTIONS A
inexpensive composites and those of most interest to the industry are particulate-reinforced MMCs. The suitability of MMCs as viable replacements for conventional monolithic materials depends on the acquisition of scientific understanding in order to synthesize them with consistent reproducibility in microstructure and mechanical behavior and their ability to exhibit enhanced performance– based cost effectiveness in real-time applications.[10] The enhanced performance of these MMCs depends on a careful selection of processing technique/parameters, matrix type, reinforcement type, and heat treatment procedure. The full potential of the metal and ceramic combination, however, is strongly influenced by the processing associated microstructural evolution.[11,12] Most work on MMCs is on light metals such as Al, because ultrahigh strength alloys are hardly strengthened by the addition of reinforcement. Recently, Mg-based c
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