A composite material is a materials system composed of a mixture or combination of
two or more micro or macro constituents that differ in form and chemical
composition and which are essentially insoluble in each other. Metal matrix
composites are engineered materials composed of an elemental or alloy matrix in
which an insoluble second phasel reinforcer is embedded and distributed to achieve
some property improvement. Particulate reinforced metal matrix composites
constitute a major portion of these advanced materials. Aluminium-silicon alloys, as
a matrix material, are characterized by lightweight, good strength-to-weight ratio,
ease of fabrication at reasonable cost, high strength at elevated temperature, good
thermal conductivity, excellent castability, good weldability, excellent corrosion
resistance and wear resistance properties. Application of particulate reinforced
composites in the aerospace, automotive, transportation and construction industries
depends on the choice of cost affordable factor. In this research work, particulate reinforced metal matrix composites are processed by vortex method, a melt stirring
liquid metallurgy technique. Four different particulates namely, graphite,
combination of tungsten carbide and aluminium silicate for hybrid composite
reinforcement, quartz and titanium carbide are used as second phase reinforcers for
reinforcement in the matrix. Aluminium-1 1.8% silicon alloy is selected as the matrix
material and the particulates are mixed in different weight fraction %. Slab
composite castings are made by pouring the composite mixture in grey cast, steel and
copper permanent-molds. Process parameters like pouring temperature, particulate
preheating temperature, impeller blade speed and shape are optimized and composite
castings containing different weight fraction % of particulate are made by
permanent-mold casting process. Effects on different weight fraction % addition of
particulate on the particulate distribution in aluminum-1 1.8% silicon alloy
composites are studied. The processed particulate reinforced composites are
subjected to mechanical tensile testing and the properties are determined for different
type of particulate reinforcements in the aluminium-11.8% silicon alloy matrix.
Besides, hardness, density, impact strength-charpy, fracture toughness, electrical
resistivity, electrical conductivity, thermal diffusivity, thermal conductivity, thermal
expansion coefficient measurements are performed by using the appropriate
equipments and machines. Metallographic studies of the processed particulate
composites are conducted by optical microscopy and photomicrographs are captured
at different magnifications to reveal and examine the particulate distribution in the
aluminium-1 1.8% silicon alloy matrix. SEM observation of the fracture surfaces of
tensile tested, charpy impact tested specimens are performed to study the fracture
mechanics and surface characteristics with the aid of captured SEM fractographs.
Interfacial bonding features of the processed composites are also analyzed with the help of SEM. Besides, slab castings without particulate addition are made and
compared with the results based on the properties and microstructural features,
particularly for the uniformity of particulate distribution in the aluminum-1 1.8%
silicon alloy base matrix. It is found that the properties of the processed particulate
reinforced aluminium-1 1.8% silicon alloy matrix composites are superior to the cast
monolithic aluminium-1 1.8% silicon alloy based on the above-mentioned properties
studies. Photomicrographs of the processed composites based on the metallographic
studies have confirmed the uniformity of particulate distribution in the aluminium-
1 1.8% silicon alloy matrix
