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

Superplasticity was found in single phase Ni-42AI alloy with initial grain size of 200 mu m under an initial strain rate of 1.25 x 10(-4) s(-1) to 2 x 10(-3) s(-1) in temperatures ranging from 1000 degrees C to 1100 degrees C. A maximum elongation of 306% was obtained under an initial strain rate of 1 x 10(-3) s(-1) at 1075 degrees C. Optical metallography (OM) observation showed that the average grain size was refined during superplastic deformation from initial 200 mu m to less than 20 mu m. 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). (c) 2006 Elsevier B.V. All rights reserved.