Superplastic behavior has been found in Fe 3Al, Fe 3Si, FeAl, Ni 3Al, NiAl and TiAl alloys with large grain sizes (>30～600μm).
Metallographic examinations show that the average grain size of large-grained
intermetallics decreases during
superplastic deformation and a much finer grain size could be obtained after superplastic deformation. Electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) observations show that there are great numbers of subgrain boundaries which form a network and among which the proportion of low and high angle boundaries increases with the increase of strain. The observed superplastic phenomenon is explained by continuously dynamic recovery and recrystallization (CDRR). During superplastic deformation, an unstable subgrain boundary network forms and these subboundaries are absorbing gliding dislocations and transform into low and high angle grain boundaries. A dislocation gliding and climbing process accommodated by subgrain boundary sliding, migration and rotation, enables the superplastic flow to proceed.