Microstructure and mechanical properties of hot pressed submicron TiB₂ powders

This paper studies the microstructure and mechanical properties of hot pressed submicron TiB₂ powders obtained from a special carbon coated precursors method. With the hot press temperature increasing from 1500 °C to 1800 °C, the relative density increases and the sample maintains a single TiB₂ phase. The powders are able to be sintered to a relative density of ~94.5% at the temperature of 1800 °C. For the first time, unique elongated platelike grain structure, which has only been observed from transient liquid phase or reaction sintered borides, also forms at the sintering temperature of 1800 °C. In addition, the sample sintered at 1800 °C has a fine microstructure (elongated grain of ~0.3–3 µm) and high mechanical properties (hardness of ~27.6 ± 2.3 GPa, flexural strength of ~560 ± 49 MPa, and fracture toughness of ~6.5 ± 0.2 MPa m^−1/2). Correlations between mechanical properties and microstructure are further discussed.