Dry Sliding Wear Behavior of $Al_2O_3//SiC$ Particle Reinforced Aluminium Based MMCs Fabricated by Stir Casting Method

$Al_2O_3//SiC$ particulate reinforced metal matrix composites were produced by a stir casting process. The $Al_2O_3//SiC$ powder mix was prepared by reaction of aqueous solution of aluminium sulphate, ammonium sulphate and water containing SiC particles at 1200°C. 10 wt% of this hybrid ceramic powder with different sized SiC particles was added to a liquid matrix alloy during a mechanical stirring between solidus and liquidus under inert conditions. Dry sliding wear tests were conducted with a pin-on-disk friction and wear tester. The morphologies of the worn surfaces were examined using a scanning electron microscope to observe the wear characteristics and investigate the wear mechanism. An optical microscope was used to examine the precipitations of the hybrid ceramic reinforced metal matrix composites after wear tests at room temperature under dry conditions. It was found that hybrid and bimodal particle reinforcement decreased weight loss especially when SiC powder with larger grain size was used. Microstructural examination showed that besides occurring coarse SiC particle reinforcement, a fine alumina particle reinforcement phase was observed within the aluminium matrix (A332). The improvement in wear resistance of the hybrid ceramic reinforced metal matrix composites could be attributed to the ability of the larger SiC particles to carry a greater portion of the applied load, as well as to the function of the larger SiC particles in protecting the smaller alumina particles from being gouged out during the wear process. Furthermore, the incorporation of hybrid and bimodal particles increased hardness of the composites with respect to the composite with fully small sized particles.