Micrometer-sized titanium carbide with properties comparable to those of nanocrystalline counterparts

Abstract

The influence of sintering pressure on the mechanical properties of bulk titanium carbide (TiC) fabricated through work hardening at high pressure and high temperature is investigated systematically. A series of pure polycrystalline TiC samples are prepared by sintering micrometer-sized TiC powders at a pressure of 9.0–14.0 GPa and a temperature of 1500 °C. These samples are then characterized by various techniques for determining their residual stress, grain size, density, microstructural defects, hardness, and fracture toughness. The results demonstrate that the Vickers hardness HV and the fracture toughness KIC depend strongly on the sintering pressure. It is found that the mechanical properties of the sintered samples improve with increasing sintering pressure. The relative density increases with increasing sintering pressure, reaching near full density at 14.0 GPa. The hardness and fracture toughness of the sample sintered at 1500 °C at 14.0 GPa pressure are 31.2 GPa and 4.2 MPa m1/2, respectively. The high-pressure and high-temperature environment causes severe plastic deformation of the grains, as well as a high density of dislocations, resulting in a dislocation pileup. The latter, together with the production of defects such as sub-boundaries and stacking faults, provides strengthening and stabilizing effects and improves the material hardness.