Sintering Behavior of Powder Metallurgy Aluminum Metal Matrix Composites

Abstract

Powder metallurgy (P/M) is a near-net-shape manufacturing process in which metallic powders are pressed and sintered into high-tolerance components. Aluminum-Silicon P/M alloys have been of particular interest as these materials offer the advantage of high-wear resistance, high strength, good temperature resistance, and a low coefficient of thermal expansion. More recently, a novel hypereutectic aluminum-silicon alloy referred to as “Alumix-231” has emerged. The first known Al-Si commercial press and sinter P/M system, this alloy is manufactured by Ecka Granules and has a nominal composition of Al-14Si-2.5Cu-0.5Mg. Aluminum metal matrix composites with SiC as a reinforcement particle has been significantly improved in terms of mechanical properties of aluminum alloys. Si and SiC have important role to improve wear properties of aluminum alloys. At this research, we optimize sintering behavior of aluminum metal matrix composites with different chemical compositions. The powder was compressed by using dual action press machine with compaction pressure from 300-700 MPa. Green density increased with increasing compaction pressure. All samples were sintered in a tube furnace under a flowing nitrogen atmosphere. Sintering temperature is from 520-570oC for 30-120 minutes and 5-15oC/min heating rate. Before reach sintering temperature, compacted powder were dewaxed at 400oC for 20 minutes. Highest sintered properties (exp. Sintered density, hardness) was obtained by using 560oC sintering temperature for ~97% sintered density. And at optical microscopy also showed highest densification on this sample. Chemical compositions at this research played an important role to improve sintering properties. Alumix 231 significantly improved sintering properties of aluminum metal matrix composites. Highest sintering density was obtained for over than 95% relative for these compositions. T6 heat treatment was carried out to observe the effect of heat treatment to the alloy. The optimum heat treatment involved solutionizing the samples at 512oC for 50 minutes, followed by water quenching, and artificially aging the samples at 173oC for 24 hours and 10 hours for another powders. Rolling of sintered samples was also done to improve mechanical properties of these materials.