Fabrication, Microstructures, and Properties of 50 vol.% SiCp/6061 Al Composites via Hot Pressing

Nearly fully dense 50 vol.% SiCp/6061 Al composites were fabricated via hot pressing (HPing) at temperatures ranging from 610 to 650 degrees C, with the axial load and holding time fixed as 25 MPa and 120 min, respectively. The interfacial reactions, microstructures, and properties of the SiCp/Al alloy were studied. The interface reaction between SiCp and the Al alloy was suppressed at annealing temperatures of 620 degrees C and below; however, the reaction intensified as the annealing temperature increased, producing Al4C3, Si, and Mg2Si. With an increase in HPing temperature from 610 to 630 degrees C, the 6061Al alloy melted and gradually filled the pores in the SiC particles under the applied load. The density, bending strength, and thermal conductivity (TC) of the composites increased, whereas the coefficient of thermal expansion (CTE) of the composites decreased. With an increase in HPing temperature increased from 630 to 650 degrees C, the 6061Al alloy melt leaked through the sintered bodies, resulting in the microstructural degradation and property reduction of the composites. The 50 vol.% SiCp/6061 Al composites fabricated by HPing at 630 degrees C exhibited optimal comprehensive properties [bending strength, 332.4MPa; TC, 186.3 W(mK)(-1); and CTE, 7.9 x 10(-6)/degrees C (20-100 degrees C)], which were attributed to the highest relative density and the best SiCp/Al interfacial structure of the composites.