Investigation of AlN addition on the microstructure and mechanical properties of TiB2 ceramics

TiB2 ceramics with AlN addition were hot pressed at the temperature of 1800 degrees C under a load of 30 MPa for 1 h to investigate the effect of AlN particles addition as a sintering aid on the densification, mechanical properties, and microstructure of TiB2. AlN addition improved the densification behavior of TiB2, and for TiB2 containing 10 wt% (13.35 vol%) AlN, the relative density of 97.5% was achieved. Mechanical properties of composites including Vickers hardness, flexural strength, and fracture toughness was measured. The Vickers hardness of 27.31 GPa was obtained for TiB2- 2.5 wt% AlN. SEM micrographs and XRD patterns of hot pressed ceramics revealed the formation of secondary BN phase in the grain boundaries as the result of the reaction between AlN and surface B2O3 impurity on the surface of TiB2 particles. Weak intergranular BN phase formation limited the flexural strength but improved the fracture toughness up to the value of 7.8 Mp. m(1/2) for TiB2-AlN ceramics. The electrical resistivity of 0.0028 Omega was obtained for TiB2- 7.5 wt% AlN.