Microstructural characterization of interface in SiC fiber-reinforced Ti-15V-3Cr-3Al-3Sn matrix composite

The detailed microstructure of the interfacial reaction layer in SiC (SCS-6) fiber-reinforced Ti-15-3 (Ti-15V-3Cr-3Al-3Sn) alloy matrix composite has been studied using transmission electron microscopy. The interfacial reaction occurs between the Ti matrix and the outermost coating layer of the SiC fiber. The reaction layer grows at the expense of both the Ti-15-3 matrix and the outermost coating layer. The reaction front on the coating layer side is relatively smooth while that adjacent to the matrix is irregular due to a difference in reaction rate between the coating layer and α, β phases of the matrix. The mean thickness of the reaction layer follows a parabolic growth law. The results of transmission electron microscopy with energy dispersive spectroscopy observations indicate that the reaction layer consists of a mixture of single crystal stoichiometric Ti₅Si₃, nonstoichiometric TiC_1-x, and the size of these reaction products varies with the location of the layer. The product size adjacent to the matrix is larger than that adjacent to the unreacted outermost coating layer. In addition, vacancy ordering in the TiC_1-x phase is identified and microvoids, which result from the volume contraction during the reaction, are also observed in the interfacial reaction layer.