Densification and Mechanical Properties of B 4 C with Al 2 O 3 as a Sintering Aid

The densification behavior and mechanical properties of B 4 C hot‐pressed at 2000°C for 1 h with additions of Al 2 O 3 up to 10 vol% were investigated. Sinterability was greatly improved by the addition of a small amount of Al 2 O 3 . The improvement was attributed to the enhanced mobility of elements through the Al 2 O 3 near the melting temperature or a reaction product formed at the grain boundaries. As a result of this improvement in the density, mechanical properties, such as hardness, elastic modulus, strength, and fracture toughness, increased remarkably. However, when the amount of Al 2 O 3 exceeded 5 vol%, the level of improvement in the mechanical properties, except for fracture toughness, was reduced presumably because of the high thermal mismatch between B 4 C and Al 2 O 3 .