Dissolution behavior of δ phase and its effects on deformation mechanism of GH4169 alloy

The evolution of δ phase during hot deformation of GH4169 alloy was investigated by optical microscopy (OM), electron backscattering diffractometry (EBSD), scanning and transmitting electron microscopy. The dissolution processes of δ phase and dynamic mechanisms were analyzed. The effect of δ phase on the mechanism of dynamic recrystallization (DRX) was discussed. The results show that, with increasing deformation temperature and decreasing strain rate, the content of δ phase decreases, but the grain size and volume fraction for dynamic recrystallization increase. The plastic deformation is mainly accommodated by bending, kinking and shearing of δ phase. Under the drive force of reduced interface energy, δ phase is transformed from needle to short needle and even sphere. The accelerated dissolution of δ phase can be attributed to the effect of dislocation, vacancy and curvature, which is concerned with the diffusion behavior of solute atoms. A larger amount of high-speed channels for the diffusion of solute atoms form due to the existence of massive defects, such as high density dislocations and vacancies, promoting the dissolution of δ phase. The main nucleation mechanisms of DRX are changed to be δ phase stimulated nucleation and discontinuous nucleation due to δ phase.