Superplasticity of single phase Ni–42Al intermetallics with large grains

Superplasticity was found in single phase Ni–42Al alloy with initial grain size of 200 μm under an initial strain rate of 1.25 × 10−4 s−1 to 2 × 10−3 s−1 in temperatures ranging from 1000 °C to 1100 °C. A maximum elongation of 306% was obtained under an initial strain rate of 1 × 10−3 s−1 at 1075 °C. Optical metallography (OM) observation showed that the average grain size was refined during superplastic deformation from initial 200 μm to less than 20 μm. Transmission electron microscopy (TEM) observation showed that an unstable subgrain boundary network was formed during superplastic deformation. The subgrain boundaries were transformed into low and high angle grain boundaries by absorbing gliding dislocations. The large-grained superplastic phenomenon could be explained by continuous dynamic recovery and recrystallization (CDRR).