Abstract
Boron carbide/titanium diboride composites with 20 and 40 vol% particulate TiB2 and various amounts of free carbon were investigated with respect to microcrack toughening. In agreement with previous work, the mere addition of TiB2 was found to raise the toughness from 2.2 MPa·m1/2 up to 3.0 and 3.5 MPa·m1/2, respectively. A further and very significant increase of composite toughness up to 6.0 MPa·m1/2 was discovered upon the incorporation of free carbon. SEM and TEM observations reveal that this toughening is associated with microcracking at B4C‐TiB2 phase boundaries. Microcracking is triggered by thin carbon interlayers, which are located at hetero interfaces and supply a weak fracture path.
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