Paper on Optimization

Aluminum matrix

* Continuous fibers: boron, silicon carbide, alumina, graphite

* Discontinuous fibers: alumina, alumina-silica

* Whiskers: silicon carbide

* Particulates: silicon carbide, boron carbide

STIR CASTING METHOD OF FABRICATION OF MMCs

* Liquid state fabrication of Metal Matrix Composites involves incorporation of dispersed phase

* into a molten matrix metal, followed by its Solidification.

* In order to provide high level of mechanical properties of the composite, good interfacial

* bonding (wetting) between the dispersed phase and the liquid matrix should be obtained.

* Wetting improvement may be achieved by coating the dispersed phase particles (fibers). Proper

* coating not only reduces interfacial energy, but also prevents chemical interaction between the

* dispersed phase and the matrix.

* The simplest and the most cost effective method of liquid state fabrication is Stir Casting.

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* Stir Casting

* Stir Casting is a liquid state method of composite materials fabrication, in which a dispersed

* phase (ceramic particles, short fibers) is mixed with a molten matrix metal by means of

* mechanical stirring.

* The liquid composite material is then cast by conventional casting methods and may also be

* processed by conventional Metal forming technologies.

* Stir Casting is characterized by the following features:

* Content of dispersed phase is limited (usually not more than 30 vol. %).

* Distribution of dispersed phase throughout the matrix is not perfectly homogeneous:

* 1. There are local clouds (clusters) of the dispersed particles (fibers);

* 2. There may be gravity segregation of the dispersed phase due to a difference in

* the densities of the dispersed and matrix phase.

* The technology is relatively simple and low cost.

* Distribution of dispersed phase may be improved if the matrix is in semi-solid condition.

* The method...