Phase transition of multi-component (TiZrVNb)C ceramics—Part II: From single phase to multiple phases via adjusting V content

In order to solve the problem that the mechanical properties of single-phase multi-component carbide ceramics are relatively mediocre, the phase transition from single phase to multiple phases was put forward to achieve superior mechanical properties. A series of (TiZrV_xNb)C_0.8 ceramics with different V content were fabricated by spark plasma sintering (SPS). The influence of the V content on the phase compositions, microstructural evolution, and mechanical properties was investigated in detail. The transition behavior from single phase to multiple phases is discovered and discussed. The formation of the Zr-rich phase and Zr-poor phase can be attributed to the increase of lattice distortion and mixed enthalpy by adding V element. The obtained nanometer lamellar structure with semi-coherent interface via in-situ decomposing is reported for the first time in multi-component carbide ceramics. The semi-coherent interfaces with the high dislocation density and strain concentration have an effective influence on the improvement of mechanical properties as well as grain refinement and multi-phase formation. The optimal comprehensive mechanical properties of Vickers’ hardness (26.3 GPa), flexural strength (369 MPa), and fracture toughness (3.1 MPa·m^1/2) are achieved in the sample with 20 mol.% V.