Superplasticity of Ni-rich single phase NiAl intermetallics with large grains

Superplastic behavior has been found in Ni-rich single phase NiAl intermetallics with large grains. The large-grained NiAl alloy exhibited deformation characteristics of most fine-grained superplastic alloys without the usual pre-requisites of a fine grain size and grain boundary sliding. Metallographic examination (OM) showed that the average grain size of large-grained NiAl alloys decreased during superplastic deformation and a much finer grain size was obtained after superplastic deformation. Transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD) observations showed that there were great numbers of subgrain boundaries which formed a network and among which the proportion of low and high angle boundaries increased with the increase of strain. The maximum elongation to fracture increases with the increase of Ni content in Ni-rich single phase NiAl intermetallics. The observed superplastic phenomenon is explained by continuous dynamic recovery and recrystallization.