Microcracking in B₄C‐TiB₂ Composites

Abstract

Boron carbideltitanium diboride composites with 20 and 40 vol% particulate TiB, and various amounts of free carbon were investigated with respect to microcrack toughening. In agreement with previous work, the mere addition of TiB, was found to raise the toughness from 2.2 MPaml" up to 3.0 and 3.5 MPam'", respectively. A further and very significant increase of composite toughness up to 6.0 MPam'" was discovered upon the incorporation of free carbon. SEM and TEM observations reveal that this toughening is associated with microcracking at B,C-TiB, phase boundaries. Microcracking is triggered by thin carbon interlayers, which are located at hetero interfaces and supply a weak fracture path.

Densification and Mechanical Properties of B4C with Al2O3 as a Sintering Aid

“…As the hardness and the elastic modulus of Ϫ6 /°C for Al 2 O 3 ) also is another factor in reducing the hardness. Sigl 15 noted that microcracks produced by thermal mismatch had a pronounced effect in decreasing the hardness.…”

The effect of B4C on the microstructure and thermo-mechanical properties of HfB2-based ceramics

“…Such microcracks were induced by the great mismatch of thermal expansion between HfB 2 and B 4 C (6.5 × 10 −6 • C −1 for HfB 2 and 4.2 × 10 −6 • C −1 for B 4 C) [16,17], and it can enhance the toughness of composite by absorbing the fracture energy. The similar microcracking mechanism was frequently observed to occur in B 4 C-TiB 2 composites [18,19].…”

Formation mechanism of B4C–TiB2–TiC ceramic composite produced by mechanical alloying of Ti–B4C powders

“…In previous studies [22][23][24], some B 4 C based composites, e.g. B 4 C/TiB 2 , B 4 C/TiB 2 /MB 2 , B 4 C/MB 2 , B 4 C/Al, B 4 C/SiC, have been developed.…”