الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Aluminium alloys with silicon as the major alloying element are the most widely used Al alloys. The eutectic phase in these alloys is formed by hard and brittle silicon plates deteriorating the toughness of the material. To enhance ductility, silicon can be modified the microstructure by addition of modifying element and high cooling rate using RST by melt –spun process as a one of the most fruitful routes for the synthesis of metallic alloys. Due to economic and environmental requirements, it is becoming increasingly important to reduce vehicle weight. for such an objective, Al-Si melt –spun process alloys have been widely employed to produce automotive components working at ambient and fairly high temperature due to excellent characteristics such as low cost manufacturing, excellent castability, high specific strength and recyclability. Cu as commonly added to improve the strength at room temperature. In the present work, a two series of Al-xSi (where x =0 ,1,5, 9, and 13 wt. %) and Al-13Si-xCu (where x = 0.1, 0.3, 0.5, 1,2,3,4 and 5 wt. %) were prepared by rapidly solidification processing using melt –spun technique. Details of the used alloys compositions are given in the table (1.). The prepared metallic ribbons were characterized via scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques. Also, young’s moduli, internal friction, thermal diffusivity and Vickers microhardness measurements of melt –spun ribbons was studied by utilizing dynamic resonance technique and Vickers tester. The collective results of this thesis demonstrate a detailed understand of the manufacture of Al-Si-Cu alloys and the mechanism of microstructure formation. The results are significance scientifically, have industrial relevance, implications in controlling the microstructure, improving the performance and reliability of Al alloys, from the results, it can be said, that there is an improvement in the mechanical properties of binary Al-Si alloys and refining for the crystallite size. But the negative response happened in the electrical resistivity measurements. by additions of Copper, we can overcome this negative response. Also, we concluded that the addition of Copper improved mechanical properties and Vickers microhardness number this is due to the formation of intermetallic compound Al2Cu and Al4Cu9 and a good enhancement for the crystallite size.