Spark Sintering Behaviors of TiB<sub>2</sub>-10Ni with Elementary Bimodal TiB<sub>2</sub> Powders

This study investigates the spark plasma sintering behavior of TiB2-10vol.%Ni powder composites, focusing on the effects of TiB2 particle size variation on microstructure and toughness. The experimental results confirm that utilizing TiB2 powders with mixed particle sizes enhances sintering performance and improves fracture toughness. Two types of TiB2 powders were used: fine TiB2 powder (STiB2, ∼3 µm) and a mixed powder containing larger TiB2 particles (LTiB2, average size ∼15 µm). These powders were mixture with Ni powder and using spark plasma sintering preparation of composite material. The sintering behaviors corresponded to the obtained characteristic microstructures, as follows: (1) For 100STiB2-10Ni, the relative density increased from the lowest temperature compared with others, which corresponds to random distribution of STiB2 and Ni. (2) For 100LTiB2-10Ni, heterogeneous area consisting of fractured particles by initial loading corresponded to high level in initial relative density. (3) For 50STiB2+50LTiB2-10Ni, there were both similar areas to in 100STiB2-10Ni and 100LTiB2-10Ni, which correspond to density increase at initial stage and sintering promotion after medium temperature. The highest final density level was obtained by deformation of continuous Ni layer in heterogeneous region, such as100LTiB2-10Ni. The sintering curve of 50STiB2+50LTiB2-10Ni could be explained by the behavior of both 100STiB2-10Ni and 100LTiB2-10Ni. Its relative density showed the highest value, and its sintering rate was close to that of pure Ni, which showed a high value. Furthermore, it was found that 50STiB2+50LTiB2-10Ni exhibited high fracture toughness values.