Microstructure evolution of C/Mo double-coated SiC fiber reinforced Ti6Al4V composites

C/Mo double-coated SiC fiber reinforced Ti6Al4V (SiCf/C/Mo/Ti6Al4V) composites fabricated by foil-fiber-foil (FFF) were thermally exposed for the purpose of investigating thermal stability of the C/Mo duplex coating at high temperatures of 700-900 °C. It is revealed in the study that the SiCf/C/Mo/Ti6Al4V composites have an excellent thermal stability at temperature below 700 °C compared to the poor thermal stability at 800 °C. When the composites were thermally exposed at 900 °C for 100 or 200 h, a large number of TiC, Ti2AlC or Ti3AlC particles were identified as reaction products in the matrix by means of energy-dispersive spectrometer analysis, X-ray diffraction analysis and transmission electron microscopy. The formation mechanism of these particular phases was analyzed in terms of thermodynamics, composition condition and element diffusion path. In addition, the longitudinal tensile performance of the composites thermally exposed under 900 °C/200 h was tested at room temperature, and the corresponding failure behavior was analyzed.