Effect of Na3AlF6 Addition and Surface Modification of SiCp on the Microstructure and Mechanical Properties of SiCp/Al Composites
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Al-matrix composites reinforced with 56.5 vol% SiC were prepared by powder metallurgy with different amounts of additives and surface modifications of SiCp. The crystalline phase, morphology, elements on the surface of SiCp and the interface between SiCp and Al were characterized by XRD, SEM, EDS and EPMA. The results show that it is favorable for the reaction between TiO2-C on the surface of SiCp and Al at the SiCp-Al interface at 1 050 °C. Besides, the process of Na3AlF6 melting, dissolving and then contacting with Al2O3 formed the NaF-AlF3-Al2O3 system, which generated OAlF2−, promoting the dessolution of Al2O3 film on the surface of Al powder. Na3AlF6 meets the needs of chemical reaction in TiO2-C-Al system at the SiCp-Al interface in the way of offering more molten Al. After 0.75 wt% Na3AlF6 was added into raw materials, the whole TiO2-C film and most SiO2 film were destroyed and the interfacial bonding between SiCp and Al was keeping good, in which no obvious void and crack were observed. Meanwhile, no brittle Al4C3 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.
Key wordsSiCp/Al composites powder metallurgy additives surface modification
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