Interfacial reaction in SiCf/Ti-6Al-4V composite by using transmission electron microscopy

The interfacial reactions of continuous SiC fiber reinforced Ti-6Al-4V matrix composite (SiCf/Ti-6Al-4V composite) and continuous SiC fiber coated by C reinforced Ti-6Al-4V matrix composite (SiCf/C/Ti-6Al-4V composite) were investigated by using micro-beam electron diffraction (MBED) and energy disperse spectroscopy (EDS) on transmission electron microscopy (TEM). The sequence of the interfacial reactions in the as-processed and exposed at 900°C for 50h SiCf/Ti-6Al-4V composites can be described as SiC||TiC||Ti5Si3 + TiC||Ti-6Al-4V and SiC||TiC||Ti5Si3||TiC||Ti5Si3||TiC||Ti5Si3||Ti-6Al-4V, respectively. Additionally, both in as-processed and exposed composites, Ti3SiC2 and Ti3Si are absent at the interfaces. For the SiCf/C/Ti-6Al-4V composite exposed at 900 °C for 50 h, the sequence of the interfacial reaction can be described as SiC||C||TiCF||TiCC||Ti-6Al-4V before C coating is completely consumed by interfacial reaction. When interfacial reaction consumes C coating completely, the sequence of the interfacial reaction can be described as SiC||TiC||Ti5Si3||TiC||Ti-6Al-4V. Furthermore, in SiCf/C/Ti-6Al-4V composite, C coating can absolutely prevent Si diffusion from SiC fiber to matrix. Basing on these results, the model of formation process of the interfacial reaction products in the composites was proposed.