Fracture in Superplastic Ceramics

Observe that temperature is an important parameter and Q is the activation energy, also given in Eq. (2.20)  

Superplastic ceramics deform without necking and fail by intergranular cracks that propagate perpendicular to the applied tensile axis. Grain size has been considered as a critical factor in superplasticity. In Fig. 8.88, fracture strain is indicated as a function of flow stress in FG ceramics, while the strain-rate sensitivity, m, remains high. In Fig. 8.88, various ceramics are plotted, (the reader is referred to the original works)  

The data in Fig. 8.91a are shown at a fixed temperature of 1823 K and at a local true strain of 0.5, while those in Fig. 8.91b are shown at a fixed strain rate of 2.7 X 10 s and local true strain of 0.5. Lq refers to the grain size in the gripping region at zero local true strain. Thus, L Lq reflects the deformation-enhanced 

Using the experimental results shown in Figs. 8.90 and 8.91, the kinetics of deformation-enhanced concurrent grain growth is  

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