الفهرس 
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Abstract
ease af fabrication. In case of particulate metal matrix composites an increase in fracture
toughness and related properties can be achieved. This type of composites can be economically
fabricated.
In recent years, various processes of liquid metal infiltration techniques such as vacuum
infiltration, pressure infiltration, squeeze casting have been applied to produce fiber or
particle reinforced composites. In these techniques the reinforcements were in the shape of
preforms. It was found that preforms have limitations in their use and their volume fraction. Some
techniques based on liquid state causes flotation, settling, segregation of pa1ticles and a thick
interfacial reaction layer between particles and matrix.
In this work, an experimental technique previously developed was used to produce PMMC by the
centrifugal casting process. This was applied to tlu·ee systems (AI 12Si 2Mg I Al203,1Graphite and
I
Feldspar) with different particle densities 2.6, 2 and 3.2 grn/cm3.
An aluminium alloy rod with a certain length is inserted in a steel capsule on the top of a
predetermined amount of loose particles. The steel capsule was inse1ted in an insulated tube and
all the system is heated to the required superheat. After heating the system, the insulated tube
containing the steel capsule is mounted on the horizontal shaft to rotate with the required
rotational speed. Some process and composite variables were changed, such as melt superheat,
rotational speed, radius of rotation and particle size.
Generally, unifonn particle distribution in the produced composite was obtained particularly in
case of alumina particles. The highest volume fraction of particles occurred in case of composites
with feldspar particles. The volume fraction of particles depended on the particle size and
infiltration pressure. The higher superheat combined with high powder preheating
temperature, coarser
particles with regular shape and higher centrifugal forces were required to achieve full
infiltration.
By increasing the melt superheat, infiltration pressure and particle size, the microporosity
(pores) nearly disappeared and highest relative density was obtained. The relative density was
affected by particle size and density. Zero voids volume fraction and void size were obtained at
the liu· end of the composite rod. Sharp .interfaces with no reaction layers and good wetting were
obtained in case of the three systems used in this work the infiltration mechanism was greatly
inOuenccd by the particle type (particle density related to the matrix density).