In the present investigation, the tensile properties of A356/Al 2 O 3 nanocomposites at both ambient and elevated temperatures were studied. The A356/Al 2 O 3 nanocomposites were fabricated using a combination between the rheocasting and squeeze casting techniques. The A356 matrix alloy was reinforced with Al 2 O 3 nanoparticulates having average sizes of 60 nm and 200 nm with different volume fractions up to 5 vol%. The results revealed that the A356/Al 2 O 3 nanocomposites exhibited better mechanical properties than the A356 monolithic alloy. Such improvement in the mechanical properties was observed at both room and elevated temperatures up to 300˚C. Increasing the volume fraction and/or reducing the size of Al 2 O 3 nanoparticulates increase both the tensile and yield strengths of the nanocomposites.

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To assess the effect of the dispersion of Al 2 O 3 nanoparticles into A356 Al alloy on both the electrical and thermal conductivities, A356/Al 2 O 3 metal matrix nanocomposites (MMNCs) were fabricated using a combination of rheocasting and squeeze casting techniques. Two different sizes of Al 2 O 3 nanoparticles were dispersed into the A356 Al alloy, typically, 60 and 200 nm with volume fractions up to 5 vol%. The effect of the nanoparticles size and volume fraction on the electrical and thermal conductivities was evaluated. The results revealed that the A356 monolithic alloy exhibited better electrical and thermal conductivities than the MMNCs. Increasing the nanoparticles size and/or the volume fraction reduces both the thermal and electrical conductivities of the MMNCs. The maximum reduction percent in the thermal and electrical conductivities, according to the A356 monolithic alloy, were about 47% and 38%, respectively. Such percentages were exhibited by A356/Al 2 O 3 MMNCs containing 5 vol% of nanoparticles having 60 and 200 nm, respectively.

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In the current study, the surface composite sheet of AA2024/al203 has been fabricated using friction stir processing technique. The processing parameters during fabrication process; such as rotation speed, travel speed and number of passes have been investigated. The number of passes has a significant effect on the mechanical properties through tensile test. The results revealed that tensile strength improved with increasing passes number.Copy Right, IJAR, 2016,. All rights reserved. …………………………………………………………………………………………………….... Introduction:-Increasing demand for improving the properties of surfaces in order to meet with design and functional requirements. Friction stir processing (FSP) is one of the techniques for fabricating surface composites and modifying microstructural features, furthermore the improvement of mechanical properties. Process parameters are the key art of Friction Stir Processing. The stirring conditions (rotational and translational speeds) are important issues in FSP to obtain the desired mechanical properties.Many researchers were discussed the relation between the process parameters and the quality of welded or processed metals according to [ 1,2,3,4 ]. The Tensile strength is found to be increased with increasing the rotational speed up to specified limit for AA6351 Al alloys as reported by [ 5 ].The tensile properties and fracture locations have been investigated by many authors [ 6,7,8 ] they are fabricated metal sheets alloy using FSP. The results are revealed that the rotational speed has a significant influence on the tensile strength as a result of improving grain refinement of the material. The mechanisms of particle refinement during FSP of pure Al, and the effect of various processing parameters on the particle refinement have been studied by [ 9 ]. The investigators reported, that amount of heat generation during FSP was increased when rotational speed increase and decrease when transverse speed increase. Fabricating AA1050/SiC surface composite using FSP technique has been investigated by [ 10 ] the author concluded that , the formation of defects are causing at higher tool rotational speeds. The surface composite sheets are investigated by [ 11,12,13,14,15,16 ], they are concluded that tool rotation speed has a major effect on the mechanical properties and microstructure refinement.The effect of multi-pass FSP on the, microstructure, micro hardness and tensile strength on the metal alloy and composites have been studied by [ 17,18,19,20,21,22 ].Multi pass FSP not only improve the mechanical properties , but also get defect-free weld through adjusting the Welding parameters, including tool rotation rate, traverse speed, spindle tilt angle, and target depth [ 23 ] . multi-pass with even step (2, 4 up to 8-pass) FSP with 100% overlap was performed by [ 24 ] The results reported that multi-pass FSP were improved tensile properties of composites including UTS, yield strength (YS) and elongation. The authors were reasoned this improvement because of reduced