Ductile Fracture in Ceramics

The dislocation structure at stage 0 may be seen in Fig. 8.84. Intersecting dislocations are visible in stage 0 the density of the dislocations is p = 8.19 X 10 m compared to 4.8 x 10 of as-received samples 

As seen from the above discussion, fracture in ductile ceramics is preceded by dislocation interactions similar to those in metals and the motion of the dislocations resembles that found in ductile materials, leading to fracture usually in stage in. It is possible that in other ductile ceramics similar events also occur. It is usually thought that ceramic materials are brittle at ambient temperatures and that fracture sets in due to crack formation and propagation, which then induces further crack opening until fracture sets in. 

In ceramics, such a mechanism is in complete contradiction to the aforementioned dislocation mechanism leading to failure. Other ductile ceramics may involve dislocations in their plastic deformation, for example MgO single 

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