High‐Toughness Silicon Carbide as Armor

Silicon carbide, with single‐edge precracked beam (SEPB) toughness greater than 7 MPa·m 1/2 , was made by hot‐pressing using Al–B–C (ABC) or Al–Y 2 O 3 (YAG) as additives. The hardness of SiC processed with a liquid phase was always less than SiC densified without a liquid phase despite having a similar or finer grain size. With increasing Al content, the ABC system changed from trans‐ to intergranular fracture with a drop in hardness and a two‐ to threefold increase in SEPB toughness. Strength and Weibull modulus for materials processed with a liquid phase were higher than those of solid‐state densified SiC. Ballistic testing, however, did not show any improvement over SiC densified with B and C additives. Depth of penetration was controlled by hardness of the SiC‐based materials, while V 50 values for 14.5 mm WC–Co cored projectiles were in the range of 720–750 m/s for all materials tested.