Production, Mechanical and Thermal Properties of Chilled Aluminum - Quartz (SiO2p) Castable Metal Matrix Composite (MMC) for Automotive Applications

Structural composite materials offer automotive engineers an excellent opportunity to produce automotive components that achieve weight savings and improved mechanical properties. This paper describes a chilled aluminum-quartz particulate composite that can be cast using metallic (copper) chills much like un-reinforced aluminum using conventional aluminum casting equipments. Unlike other metal matrix composites, this material is produced economically by a simple ingot metallurgical process. An overview of the production process is given along with the techniques used for fabricating the chilled composite. The materials mechanical and thermal properties particularly its improved strength, wear resistance, fracture toughness, hardness and lower coefficient to thermal expansion and thermal conductivity are discussed in some detail. These properties offer attractive design opportunities for a variety of automotive casting applications such as pistons, connecting rods, valves, cylinder liners and suspension members. A survey of current progress in the development and testing of such components is given. These composites were shown to provide significant weight savings over ferrous metals and aluminum alloys.

The present investigation aims at producing cast aluminum alloy-quartz particulate composites in moulds containing metallic chill by dispersing quartz particles in molten aluminum alloy above the liquidus temperature, the size of the particles dispersed being between 30 μm to 100μm. The dispersoid being added ranges from 3 to 12 vol % in steps of 3%. The resulting composites cast using chills were tested for their mechanical and thermal properties. Microstructures and SEM photographs of fractured and worn surfaces were also taken for analysis.