Abstract: A NiAl-based composite with HfB2 dispersed particles has been synthesized by mechanical alloying of Ni, Al, Hf and C powders. The formation mechanism of NiAl-HfC during milling can be attributed to two chemical reactions: Ni+AlNiAl+ΔH; Hf+C→HfC+ΔH, induced by mechanical collision in a certain period of time, which results in an abrupt exothemic reaction. Hot pressing (HP) and hot isostatic pressing (HIP) have been used to make the NiAl-10HfC compacts near fully dense. Compressive testing from room temperature to 1000℃ indicated that the yield stress of NiAl-10HfC composite is 3~4 times higher than that of cast NiAl and correspond to the MA NiAl-10TiB2 composite. In the meantime, yield strength at high temperature is dependent on strain rate, and deformation is controlled by diffusion mechanism.

Key words: NiAl composite, Hfc dispersoids, Mechanical property, Reactive milling, Microstructure