Effect of metallic dopants on the microstructure and mechanical properties of TiB2

Titanium diboride (TiB2) doped with Ni and Ta was prepared by both the standard and the rapid hot-pressing method. The obvious limitations of the pure TiB2 ceramics to be fully densified are the low inter-diffusion rates, exaggerated grain growth at temperatures exceeding 2000 °C, and micro-cracks produced after sintering causing high brittleness. There is only limited number of approaches how to improve the fracture resistance together with sinterability. The method used in this work is based on doping of the basic microstructure by nickel and tantalum metals with the aim to prepare composite systems with high density and enhanced fracture resistance. The positive influence of both dopants on the microstructure and fracture behaviour was demonstrated by means of microstructure, mechanical properties and fractographic analysis. This new approach, where the careful selection of metallic dopants is needed, led to the refinement of microstructure resulting in the increase of flexural strength above the level of 700 MPa and fracture toughness of 6.0 MPa m1/2.