Interfacial microstructure and mechanical properties of B₄C matrix composite joints diffusion bonded with Ti interlayer

Boron carbide (B₄C) matrix composites are widely used in the manufacture of bulletproof armor, atomic reactor, wear and high temperature resistant structural materials due to their high hardness, high melting point, good wear resistance, oxidation resistance and neutron absorption ability. In this paper, B₄C matrix composites(B₄C-SiC-TiB₂) were diffusion bonded with intermediate layer Ti foil. The effects of bonding temperature on the microstructure of bonding interface and mechanical properties of joint were studied. The results show that B₄C-SiC-TiB₂ composites are successfully diffusion bonded at bonding temperature 1 300-1 450 ℃, and Ti reacts with B₄C to form TiB₂ and TiC. With the increasing of bonding temperature, the reaction layer becomes thicker, but too thick reaction layer will adversely affect the shear strength of the joint. The average thickness of the reaction layer is about 5 μm when the bonding temperature is 1 300 ℃. The highest joint shear strength (100 MPa) is obtained. The reaction layer is composed of TiB₂ and TiC with high hardness (25.4 GPa) at bonding temperature 1 450 ℃.