In Situ Fabrication of B4C–NbB2 Eutectic Composites by Spark–Plasma Sintering

This contribution reports, for the first time, the sintering, microstructure and properties of in situ synthesized/consolidated eutectic composites by spark–plasma sintering (SPS). SPS involves a number of processing parameters that may be used to tailor the composition of eutectic composites. It was shown that pressure may be used as a means of controlling the eutectic formation. By changing the pressure, temperature and composition, we propose a processing route that results in the in situ formation of strengthened eutectic composites, consisting of a matrix (B₄C, and B₄C–NbB₂ composite) and also containing regularly distributed whiskers of NbB₂. The composites with the eutectic composition of 35 mol.% NbB₂ obtained by SPS exhibit a high Vickers hardness (26–27 GPa) and indentation fracture toughness (~6 MPa·m^1/2).