Synthesis of Non-Stoichiometric (TiNb)C0.5 with High Hardness and Fracture Toughness under HTHP

Abstract

Nonstoichiometric TiC0.5 and (TiNb)0.5 powders were prepared by the mechanical alloying process using Ti, Nb, and TiC powders as raw materials. Furthermore, the as-prepared TiC0.5 and (TiNb)0.5 powders were used as initial materials to fabricate TiC0.5 and (TiNb)0.5 compacts under high pressures and high temperatures (HTHP) of 5.5 GPa and 1200–1550 °C for 5 min. Phase identification and microstructure of the mechanical-alloyed powders and the sintered TiC0.5 and (TiNb)0.5 compacts were realized by an X-ray diffractometer and scanning electron microscope. The results indicate that the as-prepared TiC0.5 and (TiNb)0.5 powders have a similar crystal structure of face-centered cubic (FCC) to TiC. The sintered (TiNb)0.5 compact has good Vickers hardness (~16 GPa), and notably, excellent fracture toughness (~7.3 MPa·m1/2). The non-stoichiometric compound not only reduced the sintering temperature of covalent compounds, but also greatly enhanced the mechanical properties of the materials. Thus, we have provided a novel synthetic strategy for the production of a compound with high-strength covalent bonds.