الفهرس 
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Abstract
AA7075 Aluminum alloy has been received a special attention in aerospace and transportation industries because it provides a good combination of strength, ductility, and toughness. In this study, friction stir processing (FSP) technique is used to produce a self-lubricating AA7075-O/graphite composite surface layer. The composite layer was produced at a constant traveling speed of 50 mm/min and different rotating speeds of 400, 800, and 1200 rpm for different passes. For comparison purposes, the AA7075-O alloy was friction stir processed (FSPed) without adding graphite powder at the same processing parameters. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to investigate the microstructure. Vickers hardness and wear testing were conducted to evaluate the produced composite mechanical properties. It was observed that the dispersion of graphite particles in the surface layer of AA7075-O enhanced by increasing FSP number of passes and by increasing rotating speed from 400 to 800 rpm. The produced AA7075-O/graphite composite showed higher hardness than the AA7075-O base alloy. The highest hardness value (158 Hv) was gained for the produced AA7075-O/graphite composite processed at 800 rpm after the second FSP pass. The produced AA7075-O/graphite composites display an increase in wear resistance values over the AA7075-O FSPed alloy without adding graphite powder and the AA7075-O base alloy.