Evolution mechanisms of recrystallized grains and twins during isothermal compression and subsequent solution treatment of GH4586 superalloy

Abstract

In present study, isothermal compression, solution treatment, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) observations were carried out to correlate the microstructure and deformation-solution parameters for GH4586 superalloy. And, the recrystallized mechanisms, twin evolution, γ′ precipitation and their interaction were clearly illustrated based on the analysis of the recrystallized fraction, size of γ grains, grain boundary misorientation and length fraction of twin boundaries. The results show that the process of dynamic recrystallization is controlled by the mechanisms of sub-grain rotation and strain-induced boundary migration while the process of static recrystallization is controlled by the mechanism of subgrain boundary migration. The evolution of twin boundaries during deformation is affected by two aspects: (i) the losing of twin's identity due to higher strain; and (ii) the nucleation and growth of new twins within the DRX grains. During deformation of GH4586 superalloy, fine γ′ precipitates have a hindered effect on the recrystallization nucleated from pre-existing subgrains and twin growth. Moreover, the recrystallization process has a noticeable influence on the formation of new twins. Conversely, the existing of these twins is also beneficial for the recrystallization.