Impact response of TiB2–TiB composites

• Porosity and phase composition are key factors governing impact response of TiB2–Ti composites.
• Decreasing the TiB2 content in the composite makes it pore-free.
• Ti addition turns the composite's velocity history from two-cusp into a single-cusp.

TiB2–TiB composites with a TiB2 content that varied between 100 and 36 wt% were synthesized from TiB2 and Ti powder mixtures by the Spark Plasma Sintering (SPS) technique. The residual porosity, microstructure, phase composition and static mechanical properties of the composites (bending strength, hardness and fracture toughness) were determined using standard characterization techniques. The impact response of the composites has been studied in two series of planar impact experiments. In the first, the samples were shock loaded to an ultimate compressive stress of about 25 GPa in order to determine the materials Hugoniot elastic limit (HEL). In the second series, the composites were shock loaded by a modest, 3–4 GPa, compressive pulse with the purpose to define their spall strength.The experimental results show that both the static and the dynamic properties of the composites reflect their microstructure, residual porosity and phase composition, namely, the TiB2 fraction in the composites. Even a limited Ti addition (5 wt%) in the starting mixture allows to synthesize by an SPS process at a relatively low temperature (1550 °C), composites with elevated mechanical properties, in particular high hardness (∼2400 HV). The addition of 50 wt% of Ti (36 wt% of TiB2 in the composites) yields fully dense composites with a high fracture toughness (∼9.0 MPa m0.5). The wide range of the static and dynamic properties of the TiB2–TiB composites allows their tailor-design to specific applications.

Stress at HEL of TiB2–Ti composites (filled circles) and Ti-free ceramic (triangles) and s a function of TiB2 content. The dense commercial TiB2 is marked as ESK. The open circle corresponds to σHEL = 13.8 of a pure dense polycrystalline TiB2 is an extrapolation of the σHEL values of dense TiB2–Ti composites to zero TiB content.Figure optionsDownload high-quality image (83 K)Download as PowerPoint slide