Titanium diboride (TiB 2 ) based materials have received wide attention because of their high hardness and elastic modulus, good abrasion resistance, and superior thermal and electrical conductivity. Potential applications include high temperature structural materials, cutting tools, armour, electrodes in metal smelting and wear parts. Despite its useful properties, the application of monolithic TiB 2 is limited by poor sinterability, exaggerated grain growth at high temperature and poor oxidation resistance above 1000uC. Pure TiB 2 can be densified only at high temperatures (y2000uC), with an applied pressure generally being necessary during sintering. However, these high sintering temperatures cause abnormal grain growth and microcracks, which are detrimental to the mechanical properties. Various sinter additives are commonly added to obtain dense TiB 2 with optimised mechanical properties at lower sintering temperature. The present review surveys the current state of knowledge on development of bulk TiB 2 based materials, with particular emphasis on consolidation microstructure property relationships. Three major issues are addressed: the preparation of bulk titanium boride with metallic and non-metallic sinter additives (up to 20 wt-%), tribological properties and thermal stability of the borides. In conclusion, a perspective for future development of boride materials is provided.

In the present investigation, we explore the feasibility of using TiSi 2 as a sintering aid to densify titanium diboride (TiB 2 ) at a lower sintering temperature (o17001C). The hot-pressing experiments were conducted in the temperature range of 14001-16501C for 1 h in an argon atmosphere and TiSi 2 addition to TiB 2 was restricted up to 10 wt%, with an overall objective to densify the materials with a fine microstructure as well as to assess the feasibility of enhancing the mechanical and electrical properties. When all the materials were hot pressed at 16501C, the hot-pressed TiB 2 -X% TiSi 2 (X 5 0, 2.5, 5, 10 wt%) composites were found to be densified to more than 98% q th (theoretical density), except monolithic TiB 2 (B94% q th ). An interesting observation is the formation of a Ti 5 Si 3 phase and this phase formation is described by thermodynamically feasible sintering reactions. Our experimental results suggest that the optimal TiB 2 -5 wt% TiSi 2 composite can exhibit an excellent combination of properties, including a high hardness of 25 GPa, an elastic modulus of 518 GPa, an indentation toughness of B6 MPa . m 1/2 , a four-point flexural strength of more than 400 MPa, and an electrical resistivity of 10 lX . cm.

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