الفهرس 
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Abstract
Abstract
The objective of this research was to prepare and investigate the
functionally graded materials (FGMs) prepared from Al-Si alloys using the
centrifugal casting method. Three Al-Si alloys were selected for this purpose:
A356, A413, and A390. The casting process was performed under rotational
speeds of 300, 400 and 500 rpm, respectively. The produced graded
microstructures were studied through volume fraction calculation of the different
phases at the outer, middle and inner positions of the samples relative to the
pouring direction. Hardness measurements was carried out to evaluate the
gradation in the mechanical properties from the inner to the outer zone.
It was found that the microstructure and the mechanical properties of the
FGMs at the different positions were dependent on the centrifugal force. This was
more pronounced in A390- FGMs. where the hardness increased towards the
inner zone containing the highest volume fraction of primary Si. Grain reining of
α-Al was observed in the inner zone of A356-FGMs. In A413-FGMs, Feintermetallics
were refined gradually towards the outer zone. Heat treatment of
the prepared FGMs spherodized the eutectic Si in case of A356-FGMs and
increased the hardness from ~60 to 83 (HV). In 390-FGMs, precipitation
hardening raised the hardness by about 20 % while no improvement was observed
in A413-FGMs. These results emphasize the role of centrifugal force and heat
treatment in controlling the microstructure and the mechanical properties of Al-
Si FGMs.
Keywords:
Al-Si cast alloys; functionally graded materials; heat treatment; hardness.