Microstructure-fracture behavior correlation of toughened SiCf/SiC composites prepared by vacuum infiltration and hot pressing

A hybrid processing route based on chemical slurry stabilization, vacuum infiltration and hot pressing was adopted to fabricate tough SiCf/SiC composites. The as-received 2D-woven Tyranno (R) SiC fabric preform coated with pyrolytic carbon (PyC) was used as reinforcement. For enhanced densification, 20 layers of SiC particles-infiltrated SiC fabric and SiC green tape were stacked alternately followed by liquid phase sintering at 1750 degrees C and 20 MPa for a 2 h soaking time. Calculated amounts of Sc-nitrate (5, 7 and 10 wt%) as sintering additive were added to the composite to reduce the sintering temperature and restrict the matrix grain size. SEM analysis of thermally etched compacts confirmed that a grain size distribution in the size range 350-380 nm can be obtained for composites with 10 wt% Sc-nitrate addition. Extensive comparative analysis of the flexural strength variations of the composites was correlated with the complex fiber architecture and key failure mechanisms. An alternate method to explain and analyze the tail extension behavior in layered composites is presented in terms of the fractography results. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.