EBSD analysis of evolution of dynamic recrystallization grains and delta phase in a nickel-based superalloy during hot compressive deformation

摘要

Hot compression tests of a nickel-based superalloy with delta phase (Ni3Nb) are performed. The evolution of dynamic recrystallization (DRX) grains and delta phase, as well as the interactions between DRX grains and delta phase, is investigated. It is observed that the fraction of high-angle grain boundaries significantly increases with the increased true strain or the decreased strain rate. This attributes to the obvious DRX nucleation at relatively low strain rates or large true strains. The fraction of high-angle grain boundaries firstly increases, and then decreases-when the temperature is increased. It is related to the fact that delta phases sharply dissolute as the deformation temperature exceeds 980 degrees C, and the restricting effects of delta phases on the growth of DRX grains are significantly weaken. Meanwhile, the initial needle-like delta phases experience the distortion, dissolution and transformation into the rod-like delta phases during hot compression deformation. Besides, delta phase can easily induce high density dislocation cells, which accelerates the formation and rotation of subgrains. So, nucleation of DRX is stimulated by d phase. (C) 2016 Elsevier Ltd. All rights reserved.