Microstructures and mechanical properties of TiO₂ dispersion strengthened nickel prepared using an alloying-carbonizing-oxidation-sintering process

Nickel particles containing TiO₂ grains were successfully fabricated using mechanical carbonization of Ni₃Ti alloy powder, followed by selective oxidation of Ni-TiC to Ni-TiO₂. For comparison, Ni-TiO₂ composites were prepared using a conventional mechanical alloying method. The two powders were sintered using a spark plasma sintering system at 850, 900, 950, and 1000 °C. Structural characterization was performed using X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. The relative densities of all the sintered samples were up to 99.7% at all sintering temperatures. The average particle diameter, interparticle distance, and grain size of the matrix in the sintered Ni particle composites that contained TiO₂ grains were finer than others at all temperatures. These results imply that the alloying-carbonizing-oxidation-sintering (ACOS) process is a very promising method for refining oxide particles of oxide-dispersion-strengthened alloys. The enhanced mechanical properties such as compression yield strength and hardness of the sintered Ni-TiO₂ composite is a consequence of the refinement of oxide particles by the ACOS process.