High strength of SiC-AlN-TiB2-VC multiphase ceramics induced by interface reactions

In this work, SiC-AlN-TiB2-VC multiphase ceramics with high bending strength were prepared via spark plasma sintering (SPS) at 1900 degrees C-2100 degrees C. The effects of interface reactions and solid solution reactions on microstructure and mechanical properties of these multiphase ceramics were investigated. Results show that the densification of multiphase ceramics is promoted effectively by the addition of Y2O3. Yttrium aluminum oxide with low melting point is formed due to the reaction between Al2O3 (on the surface of AlN) and Y2O3, which promotes the densification of SiC multiphase ceramics. Solid-solution reaction and interface reaction occur between matrix (SiC) and reinforcing phases (AlN, TiB2, and VC). Furthermore, solid-solution reactions occur between SiC and AlN, between AlN and TiB2, and between TiB2 and VC. Al5C3N phase is generated by interfacial reaction between SiC and AlN. Layered, rod-like BN(C) phase is formed at grain boundaries due to the reaction between AlN and B2O3 on the surface of TiB2 particles. Mechanical strength of multiphase ceramics is improved by the formation of solid solutions and the occurrence of these interfacial reactions. When sintered at 2000 degrees C, SiC multiphase ceramics with added Y2O3 exhibit excellent properties, including relative density of 99.8 %, Vickers hardness of 27.1 GPa, and bending strength of 666 MPa.