Microstructure Of SiC Fiber Reinforced Ti-Matrix Composites

The monofilament SiC fiber reinforced titanium matrix composites (SiCf/Ti) have higher specific-strength and specific-stiffness, and keep better fatigue and creep resistance at elevated temperature. Therefore, the composites become the most promising candidates for aerospace applications. However due to the high reactivity of titanium, brittle reactive products at fiber/matrix interface are easy to form and may lead to a degradation of the mechanical properties of SiC/Ti composites. In contrast, very little was reported on the study on the microstructure of the interfacial reaction zone and titanium alloy matrix in SiC/Ti composites. Therefore, in this paper, the interfacial reaction and the microstructure of the matrix of SiC/Ti-6Al-4V (wt%) and SiC/Ti-25Al-10Nb -3V-1Mo (at%) composites were investigated by means of Scanning electron microscope, Transmission electron microscope, X-ray diffraction and Electron back-scattered diffraction.By means of Scanning electron microscope, the microstructure of composites were analyzed, on the base of analysis, the processing technique of the composite was improved. A full dense composite was obtained after amelioration. The composite is with no consolidating faults such as hole and crack. The distribution of the fibers in the composite is nearly homogeneous, which is important to the mechanical properties of the composite. The interfacial reaction in composites was investigated by scanning electron microscope, transmission electron microscope and X-ray diffraction to identify the reaction products. It is shown that formation of the interfacial reaction layers are characterized by diffusional reactions. In the present paper, many reaction products such as TiC, Ti3Si, Ti5Si3 were observed in the reaction zoneof SiC / Ti-6Al-4Vcomposite, and TiC, Ti3AlC, Ti5Si3 and Ti3SiC2 were observed in the reaction zone of SiC/Ti-25Al-10Nb-3V-1Mo composite.The thickness of C-coating and reaction zone of SiC/Ti-25Al-10Nb-3V-1Mo composites was measured by scanning electron microscope. The growth rate of C-coating and reaction zone at different temperature (700℃,800℃) were calculated, and according to the dynamics of interfacial reaction, the Q and k0 of C-coating and reaction zone were calculated, respectively.The SiC/Ti-25Al-10Nb-3V-1Mo composite was investigated by means of Electron back-scattered diffraction. The results indicate that the grain size of the matrix alloy prepared by fiber coating method is very fine. And Preferred orientation distribution was not found in the matrix alloy due to the fabrication method of the composite.