The densification behavior, microstructure and mechanical properties of bulk TiB₂-based ceramic composites, fabricated using the spark plasma sintering (SPS) technique with elements of (Fe-Ni-Ti-Al) sinter-aid were investigated. Comparing the change of shrinkage displacement of pure TiB₂ and TiB₂-5 wt% (Fe-Ni-Ti-Al), the addition of elements Fe-Ni-Ti-Al into TiB₂ can facilitate sintering of the TiB₂ ceramics. As the sintering temperature exceeds 1300 °C, the relative density does not significantly change. Alumina particles and austenite (Fe-Ni-Ti) metallic binder distributed homogeneously in the grain boundary of TiB₂ can inhibit the growth of the TiB₂ grains when the sintering temperature is below 1300 °C. The density and particle size of TiB₂ greatly influence the mechanical behavior of TiB₂-5 wt% (Fe-Ni-Ti-Al) composites. The specimen sintered at 1300 has the highest microhardness of 21.1 ± 0.1 GPa with an elastic modulus of 461.4 GPa. The content of secondary borides (M₂B, being M = Fe, Ni), which are more brittle than TiB₂ particles, can also influence the fracture toughness. The specimen sintered at 1500 °C has the highest fracture toughness of 6.16 ± 0.30 MPa·m1/2 with the smallest M₂B phase. The results obtained provide insight into fabrication of ceramic composites with improved mechanical property.
Keywords: mechanical properties; metallic additives; microstructure; spark plasma sintering; titanium diboride.