In situ fabrication of B₄ C-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-NbB ₂ 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).