Influence of Graphite Particles on Microhardness and Microstructural Behavior of AA7068 Metal Matrix Composites Processed by Powder Metallurgy

Abstract

Automotive industries require components such as automotive shock absorbers that should be lightweight and has to withstand high wear resistance. Monolithic aluminum alloys is not enough to meet the demands. Hence aluminum alloy (AA7068) reinforced with graphite particles were processed by powder metallurgy technique with different weight percentages of graphite (3, 6, and 9%) along with base matrix. A low pressure of 318 MPa was applied for compaction and sintered at a temperature of 560°C for one hour. Vickers microhardness test was carried out for measuring the microhardness of the composites. Using pin-on-disc wear-tester, wear experiments were conducted with a velocity of 1.2 m/s over a sliding distance of 2.5 km of load 5 N. Field Emission Scanning Electron Microscopy (FESEM) analysis was carried out to investigate the worn surface. Experimental results showed that the Vickers microhardness number has been reduced to 19 VHN by the addition of 9% graphite particles. Wear experiments revealed improved wear resistance by the addition of graphite particles. FESEM analysis exposed that abrasion, delamination, and oxidation were the dominant wear mechanisms for the composites. The automotive shock absorber produced using such a composite combination would be lightweight with improved wear resistance.