* For correspondence. 354 Journal of the Balkan Tribological Association Vol. 19, No 3, 354–364 ( 2013) Tribotechnics and tribomechanics MECHANICAL AND TRIBOLOGICAL BEHAVIOUR OF GRAPHITE- REINFORCED ALUMINIUM MATRIX COMPOSITES A. BARADESWARAN*, A. ELAYAPERUMAL Department of Mechanical Engineering, Madha Engineering College, 600 025 Chennai, Tamilnadu, India E-mail: barathme@yahoo.co.in; ep_mal@yahoo.com ABSTRACT In this work, mechanical and tribological behaviour of AA7075/Al 2 O 3 /graphite hybrid composite was studied. Pin-on-disc machine was used for the conductance of the wear test. The composites with 2–8 wt.% Al 2 O 3 particles were processed by conventional liquid casting method. For the hybrid composite, 5 wt.% graphite were commonly added to the base alloy. The hardness of the composites was mea- sured using a Vickers hardness tester and their tensile strength was measured by an universal testing machine (UTM). Scanning electron microscopy (SEM) was used to analyse worn surfaces of samples. It was found that an increase in Al 2 O 3 content reduced the coeficient of friction up to 6 wt.% and thereon slightly in- creased. But this effect was reverse in hybrid composites and AA 7075 / Graphite composites. Hardness and tensile strength of composites increased with increas- ing Al 2 O 3 content in both cases. The wear rates for both composites and hybrid composites were dependent on Al 2 O 3 content in the alloy. Al/Al 2 O 3 composites containing 6 wt.% Al 2 O 3 exhibited superior wear properties over the base alloy, and hybrid composites. Keywords: alloys, Al 2 O 3 , graphite, hybrid composites, AA 7075. AIMS AND BACKGROUND Aluminum alloys are an important vital engineering material for tribological and mechanical applications due to their low density, high thermal conductivity and improved machinability for automobile, aerospace, marine and mineral process- ing industries. Due to their low wear resistance they could not be applicable for many tribological applications. To overcome above, aluminum alloy – Al 2 O 3 par-