الفهرس 
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Abstract
The hypereutectic Al-Si alloys are widely used in industry for making wear-resistant castings and lightweight components such as parts of engines that reduce fuel consumption and air pollution.. Many methods have been used to improve their casting characteristics, microstructure and consequently, their mechanical properties. Ultrasonic vibration treatment during solidification of the alloy is one of these methods. The solidification hypereutectic Al–Si alloy (A392) is investigated within ultrasonic vibration with a frequency of 20.95 kHz. UV treatment induced to the melt from the bottom side of a cylindrical resin–bonded sand mold. This work aims at studying the influence of UV treatment at the different pouring temperatures of A392 alloy during solidification process on the microstructures and mechanical properties. The microstructures examination was obtained using optical microscope without and with applied UV treatment. The main parameters which including of (610, 640 and 690oC) for 600 s and different UV powers (1.1, 2 and 2.8Kw) were investigated. The results showed that the microstructures without UV treatment, the primary Si have a large faceted crystals and polygonal crystals, coarse plate-like phase with edges and corners while the eutectic silicon is found as coarse plates. With UV treatment at the pouring temperature 640oC with power 2.8 Kw at the bottom position, the primary Si particles become fine, uniform and polyhedral shaped of primary Si were obtained. Beside the microstructure modification the mechanical properties of investigated alloy are improved with UV treatment. The ultimate tensile strength (UTS) and elongation have maximum values of 140 MPa and 3.05 % respectively by comparison to the values obtained for samples produced without US vibration. The fracture surfaces of the prepared alloy without and with UV were also investigated. The improvement of hardness with UV treatment whiles the untreated samples shows high standard deviation in hardness levels. Samples with UV treated showed better wear resistance.