Present investigation discusses the relationship between formation of fiber-matrix reaction zone and fracture morphology in SiC/Ti-6Al-4V composite material. A SiC/Ti-6Al-4V composite material was fabricated by using a vacuum hot pressing method, and microscopic observations of its reaction zone and fractography of the composite on three point bending test with acoustic emission detector were carried out. The major phase present in the reaction zone was TiC. A small amount of Ti5Si3 and Ti5Si4 was detected in the zone in the as-fabricated specimens, but was not detected in the annealed specimens. The fracture stress of the composite decreased with increasing thickness of the reaction zone, and many AE events which correspond to cracking of the thick reaction zone were counted during fracturing in the bending test. Fracture morphology of the composite was different depending on the tension or compression side of specimen: in the tension side both brittle and radial types of fracture occurred while in the compression side chop marking fracture took place. The brittle type of fracture was mainly observed in the thick reaction zone. The cracking in the thick zone brings about reduction in fracture stress.
