Effects of short carbon fiber on the macro-properties, mechanical performance and microstructure of SiSiC composite fabricated by selective laser sintering

Selective laser sintering was combined with reactive melt infiltration to fabricate SiSiC part, and the effects of carbon fiber (C-f) on the properties of the SLS green body, the carbonized and final SiSiC sample were investigated. Results show that the addition of an appropriate amount of C-f (1.59 wt%similar to 2.97 wt%) can increase the bulk density and geometric precision of the sample at all stages, and improve the mechanical properties of green and carbonized samples. The main phases composed of the SiSiC composite were free Si, alpha-SiC, beta-SiC, plus a very small amount of Al-Si alloy. With 1.59 wt% C-f addition, a relatively comprehensive favorable macro-properties of both the green sample and carbonized sample was achieved, and the homogeneous microstructure of the latter favored the decreased free Si content and increased beta-SiC content of the final composite. The evolution mechanism of C-f added to the raw material is inferred to be the mutual diffusion of [C] and [Si] that occurred at the C-f/Si melt boundary leading to the formation of the siliconized C-f with relatively large diameter size (24.3 mu m) and high aspect ratio ( > 30). Amorphous C, which derived from the pyrolysis of epoxy resin E12, undergone a dissolution-precipitation mechanism with the formation of fine-grain beta-SiC.