الفهرس 
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Abstract
Friction stir processing of cast aluminum alloy Al-Si-Zn-Cu using a milling machine of 1500 rpm maximum rotation speed and 10 mm/min minimum traveling speed is studied. Test specimens are fixed on the milling machine table by a specially designed fixture. FSP is carried out at different rotation and traveling speeds (785, 1100, and 1500 rpm, as well as 10, 20, 42, 90 and 185 mm/min), while tool geometry and insertion depth of the tool shoulder are kept constant, mainly to determine suitable FSP conditions. A schedule for the determination of suitable FSP conditions is postulated to study the effect of FSP on microstructure and mechanical properties of present cast aluminum alloy Friction stir processed plates are evaluated using visual and macroscopic inspection, tensile testing, hardness measurements, and optical microscopy. The current study indicated that, FSP is an efficient method to improve the microstructure and mechanical properties of cast Al-Si-Zn -Cu aluminum alloy. Visual inspection of FSPed material indicates the presence of a limited flash size in the range 2 to 5 mm, and the top surface roughness of stir zone decreases with increasing travel and rotation speeds. Moreover, microstructure investigation reveals significant refining and precipitates fragmentation. Furthermore, a noticeable reduction in the amount of porosity relative to the base material is observed. On the other hand, the FSPed material exhibits a higher ultimate tensile strength and a larger elongation percent than the base metal. The optimum tensile properties are obtained at 1100 rpm rotation speed and 20 mm/min travel speed. As a matter of fact, at such conditions the tensile properties are dramatically improved after FSP. The ultimate tensile strength is about 4 times larger than that of the base material, while the elongation is about 2 times larger. At a constant rotation speed, increasing the travel speed increases the tensile properties due to a lower heat input during the processing thermal cycle. In addition, at a constant travel speed, increasing the rotation speed reduces the improvement in tensile properties as a result of a higher heat input. Also, FSPed material exhibits higher hardness on the top surface and on the transverse cross-section than the base material. The hardness increases with the decrease of rotation speed due to the lower heat input.