Mechanical properties of hot-pressed SiC-TiC composites
2017
SiC-TiC composites, with 0, 5, 10 and 20 vol.% of TiC, were sintered by the
hot-pressing technique at temperature of 2000°C under argon atmosphere. SiC
sintering process was activated by liquid phase created by the reaction
between Al2O3 and Y2O3, in which it is possible to dissolve passivating oxide
layers (SiO2 and TiO2) and partially SiC and TiC carbides. Microstructure
observation and density measurements confirmed that the composites were dense
with uniformly distributed components. Differences in thermal expansion
coefficients between SiC and TiC led to complex stress state occurrence.
These stresses combined with the liquid-derived separate phase between grains
boundaries increased fracture toughness of the composites, which ranged from
5.8 to 6.3MPa•m0.5. Opposite to the bending strength, fracture toughness
increased with the TiC volume fraction. By means of simulation of residual
thermal stresses in the composites, it was found that with the increasing
volume fraction of TiC, tensile stress in TiC grains is reduced
simultaneously with strong rise of compressive stresses in the matrix.
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