Effect of Na3AlF6 Addition and Surface Modification of SiCp on the Microstructure and Mechanical Properties of SiCp/Al Composites

Al-matrix composites reinforced with 56.5 vol% SiC were prepared by powder metallurgy with different amounts of additives and surface modifications of SiC p . The crystalline phase, morphology, elements on the surface of SiC p and the interface between SiC p and Al were characterized by XRD, SEM, EDS and EPMA. The results show that it is favorable for the reaction between TiO 2 -C on the surface of SiC p and Al at the SiC p -Al interface at 1 050 °C. Besides, the process of Na 3 AlF 6 melting, dissolving and then contacting with Al 2 O 3 formed the NaF-AlF 3 -Al 2 O 3 system, which generated OAlF 2− , promoting the dessolution of Al 2 O 3 film on the surface of Al powder. Na 3 AlF 6 meets the needs of chemical reaction in TiO 2 -C-Al system at the SiC p -Al interface in the way of offering more molten Al. After 0.75 wt% Na 3 AlF 6 was added into raw materials, the whole TiO 2 -C film and most SiO 2 film were destroyed and the interfacial bonding between SiC p and Al was keeping good, in which no obvious void and crack were observed. Meanwhile, no brittle Al 4 C 3 phase formed in the system. At this time, the flexure strength and density of samples presented optimal values, reaching up to 106.5 MPa and 90.77% respectively.