DZ411合金在950 ℃/190 MPa的蠕变断裂行为研究

Research on Creep Fracture Behavior of DZ411 Alloy at 950 °C/190 MPa

摘要:

通过高分辨透射电子显微镜和扫描电子显微镜对DZ411合金在950 ℃/190 MPa的蠕变行为进行了研究，解释了蠕变过程中γ′相的变形机制与应变速率之间的联系。在不同蠕变时间下，元素的定向扩散导致合金形成筏状组织，由于筏化的γ′相的长度得到了极大的延伸，其对位错的阻碍作用大大增强。因此在蠕变前期，γ′相未筏化之前，合金的应变速率较高，总应变量为0.31%，应变速率为2.78×10^–7 s^–1；当γ′相的筏化过程逐渐进行，对位错的阻碍作用也随之增大，合金便进入了稳态蠕变阶段，应变速率大大降低，总应变量为2.35%，应变速率为2.17×10^–8 s^–1；但是当合金应力积累到一定程度，位错便会以攀移的形式切入γ′相。大量位错切入γ′相，对筏化组织的连续性产生了不利影响，使得γ′相有效长度下降，对位错的阻碍作用也产生了极大的弱化，合金便进入了失稳状态，加速了蠕变过程，并最终导致合金的断裂，总应变量为17.05%，应变速率为2.22×10^–7 s^–1。

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.