BEHAVIOR OF Al_4C_3 IN Al/TiC COMPOSITES UNDER CONTROLLED HUMID ENVIRONMENT

摘要

It is generally accepted that Al_4C_3 has a negative effect in Al/SiC composites, as it tends to react with humidity in the atmosphere. Therefore, many attempts have been made to eliminate or limit the formation of Al_4C_3 using various experimental approaches. The problem of Al_4C_3 formation also applies to Al/TiC and other Al-based composites reinforced with carbides. While most of the approaches are used during processing, this work proves that post-processing techniques are also promising. In this work, Al_4C_3 was formed intentionally in Al/TiC_p composites prepared by pressureless infiltration using an L4 Taguchi experimental design, and then coated with AlF_3 via the HYSYCVD method, using Na_2SiF_6 as solid precursor. Results from the analysis by RXD and SEM show that Al_4C_3 was eliminated in the composites and that AlF_3 was formed. Tests in a controlled humidity chamber showed that after 27 days, the good condition of the composites was maintained.