Flow localization and fracture in materials exhibiting structural superplasticity

For a superplastic material which does not cavitate, fracture by rupture is expected. For superplastics which do cavitate, two modes of fracture are described depending on whether deformation remains in region II or III. If grain coarsening occurs, thermoplastic shear instabilities occur between cavities when there is a transition in mode of deformation from II to III. If deformation is stabilized in region II, shear instability is suppressed and fracture occurs by the growing together of voids according to McClintock's model