WANG Wenlong, CHEN Gang, LIU Kai, WANG Hongjie, SHEN Zhen, TIAN Zhaoyong, TAN Bo, KOU Yifei, LIU Guang
(China Academy of Ordnance Science Ningbo Branch, Ningbo 315000, Zhejiang, China)

Abstract: SiC-B4C-TiB₂ three-phase composite ceramics were prepared by using pressureless solid-phase sintering, with SiC, B₄C, TiO₂ and C as raw materials. It is found that TiO₂ can be completely converted to the TiB₂ during the sintering process. Simultaneously, densification of the SiC-B₄C composite ceramics during sintering was promoted by the increase in the content of TiB₂. The maximum relative density, bulk density and apparent porosity of the composite ceramics with 12 vol.% TiB₂ reached 97.82%, 3.12 g·cm⁻³ and 2.6%, respectively. Mechanical properties of the composite ceramics are positively correlated with their relative density. Flexural strength, Vickers hardness and fracture toughness of the samples reached (491±24) MPa, (30.1±0.8) GPa and (5.17±0.23) MPa·m^1/2, respectively. Toughening mechanism of the SiC-B₄C-TiB₂ three-phase composite ceramics was dominated by the toughening of residual thermal stresses. Mechanisms such as crack deflection and immobilisation of diffuse particulate phases were present to achieve synergistic toughening.
Key words: pressureless sintering; composite ceramics; microstructure; mechanical properties