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

Abstract

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.