In-Situ Formation of TiB₂ in B₄C Ceramics and Its Strengthening Mechanism on Mechanical Properties

To improve the mechanical properties of B₄C ceramics, TiB₂ was generated in-situ in B₄C ceramics by a reaction sintering method with TiO₂ as a sintering aid to prepare dense B₄C ceramics, and the enhancement mechanism of its mechanical properties was analyzed. The results show that the density and flexural strength of B₄C firstly increase and then decrease and the fracture toughness increases with the increase of TiO₂ addition. The density of B₄C ceramics reaches 99.6% when the TiO₂ addition is 5% (in mass fraction) and the sintering temperature is 1700 ℃. The optimum overall performance of B₄C ceramics (i.e., the Vickers hardness of 36.0 GPa, the fracture toughness of 4.38 MPa·m^1/2, the bending strength of 405 MPa) can be obtained when the amount of TiO₂ added is 15%. The in-situ TiB₂ inhibits the growth of B₄C grains, eliminates the stress at the crack tip, deflects and bifurcates the crack, and plays a role in grain refinement strengthening and toughening of B₄C ceramics.