B4C Composites with a TiB2-C Core-Shell Microstructure Produced by Self-Propagating High-Temperature Synthesis-Assisted Spark Plasma Sintering

Square-shaped boron carbide ceramic composites have been produced by spark plasma sintering with the addition of 5 to 20 vol % titanium metal powder in the B4C matrix in order to initiate an in situ self-propagating high-temperature synthesis (SHS) of TiB2. The SHS reaction not only enhances many of the physical and mechanical properties of B4C, but also reduces the required sintering temperature and pressure because of the enthalpy of reaction between metallic Ti and B4C. Sintering has been carried out in the SPS-temperature range of 1450 to 1550 degrees C with a uniaxial pressure of 40 MPa and a dwell time of 4 min under a 1 atm argon atmosphere. The effects of various amounts of Ti additions and sintering temperature on the phase composition, density, hardness, fracture toughness, and microstructure are examined. X-ray diffraction and transmission electron microscopy evaluations have shown that added Ti completely transforms into TiB2, resulting in a core-shell microstructure with a carbon core, surrounded by a TiB2 shell in the B4C matrix. Moreover, by carrying out a control experiment where TiB2 was added instead of Ti, and performing a molecular dynamics simulation of the B4C-Ti interface, the significance of the in situ SHS process has been validated.