Hot tensile deformation behaviors and fracture characteristics of a typical Ni-based superalloy

Abstract

The hot tensile deformation behaviors and fracture characteristics of a typical Ni-based superalloy are studied by uniaxial tensile tests under the deformation temperature range of 920–1040°C and strain rate range of 0.01–0.001s−1. Effects of deformation parameters on the flow behavior, microstructural evolution and fracture characteristics are discussed in detail. The results show that the flow behaviors are significantly affected by the deformation temperature, strain and strain rate. Under relatively low deformation temperatures (920, 950 and 980°C), the flow curves are composed of three distinct stages, i.e., work hardening, steady stress and flow softening stages. The flow curves show the typical DRX characteristics under relatively high deformation temperatures (1010 and 1040°C). With the increase of deformation temperature or the decrease of strain rate, the fraction of recrystallized grains increases. The synthetical effects of localized necking and microvoid coalescence cause the fracture of the studied superalloy under all the deformation conditions. δ phase (Ni3 Nb) and carbides are the nucleus for the formation of microvoids. Also, δ phase plays an important role in the coalescence of microvoids.