Strength‐Grain Size Relations in Polycrystalline Ceramics

A model is presented to explain the strength‐grain size behavior of ceramics exhibiting duplex microstructures and of ceramics with uniform coarse‐grained microstructures. Using an energy balance analysis, the model shows that in most ceramics an hitiipl flaw contained within a single large grain will initially propagate and then arrest after entering the region of increased fracture‐surface energy. The arrested flaw will subsequently propagate to failure at the value OF the critical stress intensity factor. Using the data in the literature, a strength‐(grain size) −1/2 plot for MgAl 2 O 4 was generated.