High-strength TiB-TiB2 ceramics fabricated by low-temperature sintering with mechanically milled aids

Abstract

Despite its attractive properties for applications, including in high-temperature environments, the wide use of TiB-TiB2 ceramics is hindered by its high densification temperature of >1600 °C. Herein, we clarify the effects of Ti-based sintering aids fabricated by mechanical milling on the density and strength of TiB-TiB2 by spark plasma sintering at 1300 °C, corresponding to low-temperature sintering (LTS). The particle and crystallite sizes of the aids are significant parameters for LTS and can be adjusted by mechanical milling, influencing the initial densification behavior. TiB-TiB2 fabricated with 6 wt % of milled Ti aid with particle and crystallite sizes of ∼15 μm and ∼4 nm exhibited 98.9% of the theoretical density and flexural strength of 566.8 ± 170.0 MPa. These values are comparable to those typically fabricated at temperatures >1650 °C. Notably, the TiB generated during sintering enhances the bond strength of the TiB2 grains, resulting in the fracture surface changing from intergranular to transgranular patterns. Hence, the mechanically milled aid improved the mechanical performance of the TiB-TiB2 ceramics through the combined effects of flaw elimination by densification and bond strengthening by TiB formation.