Production and Characterization of AA7075-Graphite Composite Using Friction Stir Processing

AA 7075 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/graphite composite. The composite was produced at different rotating speeds of 400, 800, and 1200 rpm with a constant traveling speed of 50 mm/min and 3⁰ tilt angle applied for one and two passes for each condition. Optical microscopy (OM), and scanning electron microscopy (SEM) were used to investigate microstructure. Vickers hardness and wear testing were conducted to the composite specimens. It was obtained that the dispersion of graphite particles in the AA7075 Al alloy enhanced by increasing both rotating speed and number of passes. The produced AA7075/graphite composite showed higher hardness and wear resistance than the AA7075 base alloy. The highest hardness value (156.2 Hv) was gained for the produced AA7075/graphite composite at 800 rpm rotating speed after FSP second pass comparing to base metal (79 Hv). Whereas, the higher wear resistance value was obtained for the processed composite at 800 rpm after the FSP first pass.