On Interfacial Microstructure Evolution in an Isothermally Exposed SiC Fiber-Reinforced Ti-17 Matrix Composite

The kinetics and mechanisms of interface reactions in a unidirectional continuous SiC fiber-reinforced Ti-17 matrix composite were investigated using transmission electron microscopy and scanning electron microscopy. It was found that a reaction zone (RZ) consisting of two-layered TiC-type carbide forms at the fiber/matrix interface during fabrication of the composite. After isothermal exposure at elevated temperatures, the two-layered TiC-type carbide is inherited, and a new TiC-type carbide layer forms within the RZ after exposure at temperatures lower than 900 degrees C, while a new Ti3C2-type carbide layer forms after exposure at 900 degrees C. It was also observed that the growth of RZ is a diffusion-controlled and temperature-dependent process, obeying the Fick's law-based parabolic relationship and the Arrhenius equation. Two material constants, the temperature-independent rate constant k(0) and activation energy Q, are determined as 31.5 x 10(-4)mu m/s(1/2) and 49.9 kJ/mol, respectively.