Bulks of Al-B-C obtained by reactively spark plasma sintering and impact properties by Split Hopkinson Pressure Bar

Mixtures of B 4 C, α-AlB 12 and B powders were reactively spark plasma sintered at 1800 °C. Crystalline and amorphous boron powders were used. Samples were tested for their impact behavior by the Split Hopkinson Pressure Bar method. When the ratio R = B 4 C/α-AlB 12 ≥ 1.3 for a constant B-amount, the major phase in the samples was the orthorhombic AlB 24 C 4 , and when R < 1 the amount of AlB 24 C 4 significantly decreased. Predictions that AlB 24 C 4 has the best mechanical impact properties since it is the most compact and close to the ideal cubic packing among the Al-B-C phases containing B 12 -type icosahedra were partially confirmed. Namely, the highest values of the Vickers hardness (32.4 GPa), dynamic strength (1323 MPa), strain and toughness were determined for the samples with R = 1.3, i.e., for the samples with a high amount of AlB 24 C 4 . However, the existence of a maximum, detectable especially in the dynamic strength vs. R , indicated the additional influence of the phases and the composite’s microstructure in the samples. The type of boron does not influence the dependencies of the indicated mechanical parameters with R , but the curves are shifted to slightly higher values for the samples in which amorphous boron was used.