Tyranno ZMI fiber/TiSi2-Si matrix composites for high-temperature structural applications

A Tyranno ZMI fiber/TiSi2-Si matrix composite was fabricated via melt infiltration (MI) of a Si-16at%Ti alloy at 1375 °C under vacuum. The Si-Ti alloy was used as an infiltrant to conduct MI processing below 1400 °C and inhibit the strength degradation of the amorphous SiC fibers. The alloy matrix formed was dense and comprised primarily of TiSi2-Si eutectic structures. The TiSi2-Si matrix composite melt-infiltrated at 1375 °C showed a pseudo-plastic tensile stress-strain behavior followed by final fracture at ∼290 MPa and ∼0.9% strain. When the MI temperature was increased to 1450 °C, however, substantial reduction in the stiffness and ultimate strength occurred under tensile loading. Microstructural observations revealed that these degradations were attributed to the damages that occurred on the reinforcing fibers and pyrolytic carbon interfaces during the MI process. The present experimental results clearly demonstrated the effectiveness of the low-temperature MI process in strengthening Tyranno ZMI fiber composites and reducing the processing cost.