Microstructure of Matrix γ-TiAl in SiCf/Ti-43Al-9V Composites

SiCf/Ti-43Al-9V composite was fabricated by a foil-fiber-foil method and vacuum hot-pressing under the condition of 1150 degrees C/150 MPa/30 min, and the microstructure of the composite was investigated by means of optical microscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. Results show that SiC fiber reacts with TiAl matrix during the consolidation and a certain thickness interfacial reaction layer is formed; the microstructure of the matrix alloy is equiaxial grain, and the average grain size is about 8 mu m, which is finer than that in the original TiAl alloy; the transformation of microstructures of the matrix alloy from reaction layer to distant matrix is a layer of gamma phase -> a mixed structure composed of alpha(2)/gamma lamellae, gamma grains and B-2 particles along grains. The thickness of gamma layer is 2 similar to 4 mu m and it is distributed around the SiC fiber. According to Ti-Al-V ternary phase diagram and diffusion of C and V atoms, the formation of these two matrix regions were analyzed. And the change of grain size in composite matrix was explained by the plasticity deformation and accumulation of deformation energy.