Abstract
TiB2-B4C composites were fabricated by pressureless sintering at 1600°C using Ni and C as densification aids. X-ray diffraction revealed the presence of TiB2, B4C and NiB. Up to 20vol% B4C additive content, dense composites with -94% of the theoretical density were obtained. The dispersion of B4C particles inhibited the grain growth of TiB2 and improved the fracture toughness and bending strength. The maximum fracture toughness and bending strength of the composites were 6.1MPa⋅m1/2 and 530MPa, respectively, in contrast with 5.1MPa⋅m1/2 and 380MPa for a sintered body without B4C. The crack deflection by B4C particles was considered to be the main toughening mechanism for this composite system. With increasing B4C additive content, the thermal expansion coefficient of the composites decreased and the electrical resistivity increased. The relation between the resistivity and composition was discussed based on the effective medium theory.
