Effect of Alumina on the Structure and Mechanical Properties of Spark Plasma Sintered Boron Carbide

Abstract

Uniform densification of relatively thick (~7 mm) consolidated boron carbide plates at relatively low temperatures (e.g. 1800°C) and low facture toughness are two of the primary challenges for further development of boron carbide applications. This work reports that these two challenges can be overcome simultaneously by adding 5 wt% alumina as a sintering aid. Nearly fully dense (97%), fine grained boron carbide (B 4 C) samples were produced using spark plasma sintering at 1700°C and above in the B 4 C‐5 wt% Al 2 O 3 system. The alumina and boron carbide matrix reacted to form an Al 5 O 6 BO 3 (a mullite‐like phase) during sintering. The Al 5 O 6 BO 3 phase facilitated uniform densification via liquid phase sintering. This secondary phase is dispersed throughout the intergranular pores, providing obstacles for crack propagation and resulting in tougher boron carbide ceramics.