Multitoughening of B_4C Composite

B4C-35vol% TiB2 composite ceramics with various amounts of free carbon hot-pressed at2070℃ were studied. The incorporation of particulate TiB2 into B4C raised the toughness from3.6MPa.m1/2 to 6.5MPa.m1/2. A further increase of composite toughness up to 7.6MPa.m1/2 wasobtAlNed upon the addition of free carbon. SEM and TEM investigation revealed that the improvement of the composite toughness resulted from the multitoughening of both the crack deflectionassociated with the incorporation of TiB2 particles and the produced microcrack nucleated due tothe strong residual stress and weak interface caused by the presence of free carbon in the interfaceand propagated along B4C-TiB2 interfaces.