Room and high temperature toughening in directionally solidified B4C-TiB2 eutectic composites by Si doping

Directionally solidified В4С-TiB2 eutectics doped with different Si contents were prepared by floating zone method. Silicon doping (up to 3 vol.%) promotes a more coherent interface between B4C matrix and TiB2 inclusions, a decrease of the spacing between TiB2 (when solidification rate is constant), and formation of a more uniform morphology with thinner inclusions. These features lead to simultaneous enhancement of Vickers hardness (HV), fracture toughness (K1c) and bending strength (σ) when compared with Si-free В4С-TiB2 eutectics. For our materials, the average HV, K1c and σ were 45.2 GPa, 7.04 MPa m1/2, and 460 MPa at room temperature or 487 MPa at 1600 °C, respectively. The values of σ at indicated temperatures are approximately twice higher than for the Si-free В4С-TiB2 eutectic composites.