INVESTIGATION OF NIAL-TIB2 IN-SITU COMPOSITES

A hot-pressing aided exothermic synthesis (HPES) technique to fabricat e NiAl matrix composites containing 0 and 20 vol. % TiB2 particles was developed. The conversion of mixtures of elements to the product was complete after processing, and TiB2 particles in the matrix were unifo rmly dispersed. The microstructure and interfaces were very thermally stable. The interfaces between NiAl and TiB2 were atomically flat, sha rp, and generally free from interfacial phases. In some cases, however , thin amorphous layers existed at NiAl/TiB2 interfaces. At least thre e kinds of orientation relationships between TiB2 and NiAl were observ ed. The compressive yield strengths at room temperature and at 1000 de grees C of the composite were approximately three times as strong as t hose of the unreinforced NiAl. The tensile yield strength at 980 degre es C of the composite was about three times stronger than that of NiAl . The ambient fracture toughness of the composite was slightly greater than that of the monolithic NiAl.