Thesis (Ph.D.) - Cairo University - Faculty of Engineering - Department of Metallurgical Engineering

In recent years, Aluminium {u2013}Silicon alloy are finding on increased industrial uses. Their low thermal expansion, high conductivity and relatively low density, when combined with good mechanical properties, make them suitable for several engineering application. It reserve these alloys require treatment to refine the Ü- aluminium matrix and modifier the eutectic Si. Different methods have been applied to improve their casting characteristics, their microstructure and consequently, their mechanical properties. Application of ultrasonic vibration to the bottom of the mould during solidification of the alloy is one of these methods. This work aimed at studing the effect of ultrasonic treatment on the properties of aluminium {u2013}silicon alloy A356 in addition to its combined effect with addition of Sb and / or AlTiB. Microstructure characterization was performed using optical and scanning electron microscopy. Ultrasonic vibration has proven to be effective in controlling columnar dendritic structure, reducing the size of equiaxed grains, and under some conditions, producing globular non-dendritic grains. An experimental apparatus which supplied a powerful 3200 Watts and frequency a 22.4 KHz of ultrasonic power was used in this investigation

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