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 degrees C to 1800 degrees 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 similar to 94.5% at the temperature of 1800 degrees 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 degrees C. In addition, the sample sintered at 1800 degrees C has a fine microstructure (elongated grain of similar to 0.3-3 mu m) and high mechanical properties (hardness of similar to 27.6 +/- 2.3 GPa, flexural strength of similar to 560 +/- 49 MPa, and fracture toughness of similar to 6.5 +/- 0.2 MPa m(-1/2)). Correlations between mechanical properties and microstructure are further discussed.