الفهرس 
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Abstract
In the present study, A356 aluminium alloy was reinforced with TiO2.particles using liquid metallurgy route (vortex method). In addition to the
monolithic matrix alloy A356, two composite materials having 10% and 20%
weight percents of TiO2 particles were prepared. The effect of the TiO2 particles
weight percent on the microstructure, aging behaviour, hardness and wear
resistance of the A356/TiO2 composites were evaluated.
Examination of the microstructure of the composites showed that the
porosity content of the composites is higher than the matrix alloy. Increasing the
weight percent of TiO2 particles increases the bulk porosity of the composites.
The top of the cast composite ingots exhibited the lower density when compared
with the middle and bottom of the ingot. The bottom of the composite ingots
exhibited the highest density.
The hardness test results showed that, incorporation of TiO2 particles into
A356 alloy increases the hardness of the alloy. The hardness of the composites
increases with increasing of weight percent of TiO2 particles. An accelerated
aging response was observed in composites. In general, it was found that the
addition of TiO2 particles accelerates the aging kinetics and reduces the time
required to reach the peak hardness.
Dry sliding wear behavior of A356 aluminum alloy composites reinforced
with the TiO2 particles were investigated by using a pin-on-ring wear tester. Pins
of the composites were rubbed against SS 316 stainless steel ring at various
sliding velocities and applied pressures. The wear resistance of composites was
improved by the presence of TiO2 particles. The results obtained from wear tests
showed that, the composites has better wear resistance as compared to the
unreinforced A356 matrix alloy.