Experimental investigation of hardness and effect of wear on sintered composites containing AA6061 matrix and TiB2/Al2O3reinforcements

Abstract

Materials prepared using powder metallurgy route exhibit dimensional stability which is required to manufacture critical parts such as brake pads, inlet valves and nozzles. In this paper, composite materials consisting of 5 and 10 wt. % of Titanium-diboride reinforcement in AA6061 aluminium alloy was produced by the sintering process via green compaction. 2 wt. % of alumina was added as the secondary reinforcement to produce the hybrid composites. The produced composites and its hybrid were compared with the base material AA6061 to determine the changes in its density, wear and hardness. The green density and sintered density of the composites and its hybrids reduced by as much as 8.47 % compared to the respective theoretical density. Microscopic examinations showed that the addition of alumina with the Titanium-diboride reinforcement increased the wear resistance of the hybrid composites by 1.22 % compared to the base material. The hardness of the sintered composite increased with the addition of the two reinforcement materials. The hardness for the hybrid composite increased by 74.94 % compared to the base material. After wear test, the hardness of the base material reduced by 6.83 % but the hardness of hybrid composite having the highest composition of both reinforcement particles increased by 6.36 %. The study revealed that the sintering process and subsequent hardening of the composites and its hybrid enhance its hardness property compared to the base material. Interestingly, the wear which leads to the changes in its tribological properties increased the hardness property of the composite and its hybrid.