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matrix composite (MMC) enhances this lightweight material with improved mechanical property attri- butes for stiffness, vibration damp- ening, wear resistance, high thermal conductivity and low coefficient of thermal expansion. With its unique set of properties, MMC has been employed in diverse applications such as moving structures in high speed equipment for manufacturing, brake rotors for vehicles, heat sinks for electronics, and housings and mirrors for optics.


T


In the 1980s and 1990s, cast- ing shapes from MMC ingot was envisioned to be a major enabling technology for manufacturing MMC metal components. This


he particulate silicon carbide reinforcement in aluminum alloy metal


perception prompted the develop- ment of metalcasting processes and specialized techniques to overcome the natural tendency of the silicon carbide particles to clump or pre- cipitate from the aluminum matrix. The inherent abrasiveness of the silicon carbide particulates in the alloy also gave MMC a reputation, perhaps unfairly, for being diffi- cult and expensive to machine. For myriad reasons, a broad market for cast and other process shapes has not developed, and so, despite its many attributes, MMC remains an underutilized material option. As with other materials that are


difficult to machine, the near-net- shape capability of investment cast- ing is an effective counterbalance to help mitigate the cost of machining aluminum MMC. With effective


casting designs, this capability, com- bined with refinements in the alloy and in secondary machining, makes investment cast aluminum alloy/ silicon carbide particulates a viable and affordable option for engineers to incorporate lightweight MMC shapes into their products.


Cast Metal Matrix Composites Although increasing development


activities have led to system solutions using metal composite materials, the use of especially innovative systems, particularly in the area of light metals, has not been realized. Te reason for this is insufficient process stability and reliability. Combined with production and processing problems, it results in inadequate economic efficiency. Application areas are cost orientated and conservative. Often, the industry


30 | MODERN CASTING January 2015


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