Plasticity of single-phase Ni-50Al intermetallics with large grains at high temperature

Abstract

High temperature deformation behavior of single-phase Ni-50Al intermetallics with initial grain size of 220 μm was examined. It was found that the alloy exhibits plastic behavior under an initial strain rate of 7.5 × 10 −4 s −1 to 1 × 10 −3 s −1 in a temperature range of 1000–1100 °C. A maximum elongation of 139% was obtained under an initial strain rate of 8.75 × 10 −4 s −1 at 1075 °C. The strain rate sensitivity, m value, is correlated with temperature and initial strain rate, being in the range of 0.16–0.263. Optical metallography (OM) showed that the grains were refined during plastic deformation from an initial size of 220 μm to less than 30 μm. Electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) observations showed that an unstable subgrain boundary network formed during plastic deformation. The sub-grain boundaries were transformed into low and high angle grain boundaries by absorbing gliding dislocations. The large grained plastic phenomenon could be explained by continuous dynamic recovery and recrystallization (CDRR).