Influence of heat treatment on microstructure and mechanical properties of Cansas-II SiC/PyC/CVI-SiC mini-composites

The influence of heat treatment at 1300 degrees C and 1500 degrees C for 50h on the microstructure and mechanical properties of Cansas-II SiC/PyC/CVI SiC mini-composites was studied in detail. The interfacial shear strength decreases from 98.8 MPa to 13.6 MPa after the heat treatment at 1500 degrees C for 50h, which was mainly caused by the weak bonding between the SiC matrix and PyC interface due to the decomposition reactions and carbothermic reductions of CVI SiC matrix. The average tensile strength of fibers decreases with the rise of heat treatment temperature, which was primarily attributed to the significant growth of beta-SiC grains accompanied by the decomposition of SiCxOy. Due to the protective effect of the PyC interface and CVI SiC matrix on the fibers, the fraction of declined strength of the mini-composites is only 25.8% after the heat treatment at 1500 degrees C for 50h.