Processing of in-situ SiC reinforced AlN based composites

In this study, highly dense (>97%) in-situ SiC reinforced AlN based ceramic-metal composites were produced by pressureless reactive infiltration of 7075 aluminium alloys into porous alpha-Si3N4, alpha-Si3N4 + 4 wt. % carbon and alpha-Si3N4 + 8 wt. % carbon preforms at 1400 degrees C for 4 hours under an argon gas atmosphere. X-ray diffraction and transmission electron microscopy analysis of the designed alpha-Si3N4-Al and alpha-Si3N4-C-Al composites revealed that Si3N4 was completely consumed during the infiltration process via reacting with the Al alloy and resulted in the formation of AlN and Si phases. The aim of the current work was to introduce a novel method to produce in-situ SiC reinforced AlN based ceramic-metal composites. Composites with relatively low metal contents were successfully fabricated through incorporating active carbon to the starting alpha-Si3N4 powder, which in turn consumes the liberated metallic Si phase in the system via chemical reactions leading to the formation of SiC ceramic phase. Formation of in-situ SiC, AlN and metallic Si were also confirmed by analytical transmission electron microscopy investigations.