الفهرس 
Chapter One: IntroductionOnly 14 pages are availabe for public view
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Abstract
Aluminum, as a base metal in metal matrix composites (MMCs), is favorite than other traditional materials in the scopes of aviation, space, automotive and marine applications because of their improved properties such as specific strength, good resistance in wear etc.
The main objective of the work is to optimize stir casting parameters, stirring speed, and stirring duration, to produce best composite of aluminum alloy 6061 reinforced by particles of Titanium dioxide (TiO2) in terms of the strength of the produced composite. Aluminum alloy of Al6061 as a matrix material is reinforced with preheated TiO2 particles with weight charges of 1, 2, 3, 4 and 5 %. The mix was then casted into a heated cylindrical steel mold to form the specimens.
Microstructural investigation was performed to ensure homogeneous presence of reinforcement particles and explore the grain sizes post reinforcing. The composites were subjected to set of mechanical investigations. The tensile and hardness tests were performed to investigate the mechanical response of composites.
Based on the microstructural results, it was found that particles homogeneously distributed. This besides grain refinement. Further hardness and tensile strength were shown higher results than the base matrix.
Wear behavior, as a major inferiority of Al6061, was tested after adding TiO2 particles constituting a reinforced composite. Composites reinforced with mass percentages 1 to 5 wt.% of TiO2 in step of 1% prepared at the optimum conditions of stir casting technique were under testing.
Pin-on-disc device was utilized to assess the wear behavior of the prepared composites at the dry state. Load was varied from 6 to 18N while the sliding distance was also varied over the distances from 500 to 2000 m at two different sliding speeds 4.5 and 6.5 m/s. Coefficient of friction and weight loss were evaluated over a spectrum of wear testing conditions.
It had shown considerable improvement of wear behavior of Al6061 in terms of coefficient of friction and weight loss. Investigation of worn surfaces of specimens was occurred using optical microscope giving clear answers for circumstances of wear process of composites.