Creep property and microstructural evolution of DD11 alloy under high temperature and low stress

In this paper, the interrupted and ruptured creep tests were carried out in a novel second generation single crystal superalloy named DD11 at 1100 °C/130 MPa. The alloy exhibited typical creep curve including primary, steady, and tertiary three creep stages. The microstructural evolution at different stages of the creep were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the γ′ phases transform into rafted structure at the early stage of the steady creep and keep stable during the steady creep stage. As the creep goes on, the rafted structure further coarsens and the topological inversion occurs. In addition, at the primary creep, the dislocations mainly move in the γ matrix and pile up in the γ/γ′ interface since the matrix channels widen slightly. The formation of the regular interfacial dislocation networks occurs at the early stage of the steady creep. Under the low stress, the dominated deformation mechanism during steady creep stage is the climbing of the 〈010〉 type edge dislocation. Furthermore, the effect of the deformation mechanism on creep property was discussed in detail.