Effects of Co content in TiO₂–Co composite prepared by alloying–recomposition–oxidation–sintering process on its mechanical properties and microstructure

TiO₂–Co composite powders with various Co contents were prepared by the alloying-recomposition-oxidation-sintering process. For comparison, conventionally mixed TiO₂–Co composites with the same compositions were sintered at 1000, 1100, 1200, 1300, and 1400℃. Structural characterizations were performed using X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive spectroscopy, and transmission electron microscopy. All of the sintered samples were more densified. A melted matrix was observed at a temperature higher than 1300℃. The flexural strength and the fracture toughness of the TCA sample were higher than those of the conventionally mixed TiO₂–Co sample at the same sintering temperature, while the Vickers hardness exhibited the opposite relationship. The flexural strength and the fracture toughness of the TCA sample increased until a Co content of 14 vol%, followed by decrease at 18 vol%, while those of the conventionally mixed TiO₂–Co sample increased in the entire Co content range. The highest flexural strength and fracture toughness were observed for T14CA sintered at 1400℃ (161.3 MPa and 6.39 MPa m^−1/2, respectively). Consequently, the desirable Co content in the TiO₂–Co composite prepared by the alloying–recomposition–oxidation–sintering process was 14 vol%.