Abstract:The creep behavior of the DZ411 alloy at 950 ℃ and 190 MPa was investigated using high-resolution transmission electron microscopy and scanning electron microscopy. The relationship between the deformation mechanism of the γ′ phase and the strain rate during creep was elucidated. With various creep durations, the alloy forms a raft structure due to the directional diffusion of elements. Because the length of the rafted γ′ phase is significantly extended, the impeding effect on dislocations is greatly increased. Consequently, in the early stage of creep and before the rafting of the γ′ phase, the alloy exhibits a higher strain rate, with a total strain variation of 0.31% and a strain rate of 2.78×10–7 s–1. As the rafting process of the γ′ phase progresses, the impeding effect on dislocations also increases, causing the alloy to enter a steady-state creep phase. In this phase, the strain rate significantly decreases, with a total strain variation of 2.35% and a strain rate of 2.17×10–8 s–1. However, when the stress in the alloy accumulates to a certain extent, dislocations will enter the γ′ phase through a climbing mechanism. A large number of dislocations cutting into the γ′ phase adversely affect the continuity of the raft structure, reducing the effective length of the γ′ phase, significantly weakening the impeding effect of the dislocations, and causing the alloy to enter an unstable state. This accelerates the creep process and ultimately leads to the fracture of the alloy. The total strain variation in this stage is 17.05%, with a strain rate of 2.22×10–7 s–1.