The microstructural evolution in large-grained Ni–40Al during superplastic deformation

Superplastic behavior has been found in Ni–40Al intermetallics with large grains. The large-grained Ni–40Al alloy exhibited all deformation characteristics of conventional fine-grained superplastic alloys. Metallographic examination (OM) showed that the average grain size of large-grained Ni–40Al alloys decreased during superplastic deformation from 220 μm before deformation to 25 μm after deformation to fracture. Electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) showed that there were a great number of sub-grain boundaries which formed a network and among which the proportion of low and high angle boundaries increased with the increase of strain. The observed superplastic phenomenon is explained by continuous recovery and recrystallization.