Investigation of NiAl–TiB₂in situcomposites

A hot-pressing aided exothermic synthesis (HPES) technique to fabricate 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 uniformly dispersed. The microstructure and interfaces were very thermally stable. The interfaces between NiAl and TiB₂ were atomically flat, sharp, and generally free from interfacial phases. In some cases, however, thin amorphous layers existed at NiAl/TiB₂ interfaces. At least three kinds of orientation relationships between TiB₂ and NiAl were observed. The compressive yield strengths at room temperature and at 1000 °C of the composite were approximately three times as strong as those of the unreinforced NiAl. The tensile yield strength at 980 °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.