Effect of TiB₂ content on microstructure and mechanical properties of in-situ fabricated TiB₂/B₄C composites

WANG Yu-jin^{1, 2}, PENG Hua-xin², YE Feng¹, ZHOU Yu¹

(1. Institute for Advanced Ceramics, School of Materials Science and Engineering,
Harbin Institute of Technology, Harbin 150001, China;
2. Advanced Composites Centre for Innovation and Science (ACCIS), Department of Aerospace Engineering,
Faculty of Engineering, University of Bristol, Queens Building, University Walk, Bristol BS8 1TR, UK)

Abstract:The fully dense boron carbide matrix composites containing 10%-40% (volume fraction) TiB₂(TiB₂/B₄C) were in-situ fabricated via chemical reaction of B₄C, TiO₂ and graphite powders at 2 050 °C under a pressure of 35 MPa. Scanning electron microscopy (SEM) and transmission election microscopy (TEM) observations show that the sub-micron/nano-sized TiB₂ particles are uniformly located within the matrix grains and at the B₄C grain boundaries. With the increase of TiB₂ content, the elastic modulus and fracture toughness of composites increase remarkably. However, the situation is reversed for Vickers hardness and flexural strength. The fracture toughness exhibits a maximum value of 8.2 MPa×m^1/2 for the 40% (volume fraction) TiB₂/B₄C composite. The main toughening mechanisms of TiB₂/B₄C composites are microcrack toughening and crack deflection toughening.

Key words:TiB₂/B₄C composites; in-situ reaction; toughening mechanisms