Production of Aluminum-Silicon Carbide Composites Using Powder Metallurgy at Sintering Temperatures Above the Aluminum Melting Point

Abstract

Abstract The extensive utilization of aluminum reinforced with silicon carbide in different structural applications has motivated the need to find a cost effective technological production method for these composites. Homogeneity, machinability, and interfacial reaction of the constituents represent the significant problems pertaining to these composites. Production of a homogenous, high strength, and net-shape structural components made from aluminum-silicon carbide composites can be achieved using powder metallurgy (PM) technology. In the present work the problem of low strength of the aluminum-silicon carbide produced by powder metallurgy is solved by raising the sintering temperature of the composite above the melting temperature of the aluminum. This method produces a local fusing and welding of the aluminum particles. Using aluminum powder with a thick oxide layer surrounding the particles prevents the total melting of the composite. Green compacted specimens containing 0, 5, 10, 15, 20, 25, and 30 wt % silicon carbide were prepared. Samples from each composition were sintered at 650, 700, 750, 800, 850, and 900°C separately, while other specimens were left without sintering for comparison. Microstructure examination, a microhardness test, and a compression test were carried out for each of the 49 combinations of SiC contents and sintering temperatures to study the effect of sintering temperature and SiC contents on the composite properties and to detect the optimum sintering temperature for each SiC weight percent. Generally the results show the tendency for both strength and ductility to increase upon increase in the sintering temperature. These specific sintering temperature levels are found to be 650°C for the aluminum with no silicon carbide content, 700°C for composites containing both 5 and 10 wt % SiC, 750°C for composites containing 15 wt % SiC, 800°C for composites containing 20 wt % SiC, 850°C for composites containing 25 wt % SiC, and 900°C for composites containing 30 wt % SiC.