Creep behavior of a 4.5%-Re single crystal nickel-based superalloy at intermediate temperatures

By means of creep properties measurement and microstructure observation, an investigation has been made into creep behavior of a 4.5%-Re single crystal nickel-base superalloy at intermediate temperatures. Results show that, after fully heat treated, the microstructure of the alloy consists of cubic γ′ phase embedded coherent in γ matrix. During creep at 760 °C/800 MPa, no rafted feature of γ′ phase is detected, but the twisted extent of the cubical γ′ phase in the regions near fracture increases. In the ranges of the applied stresses and temperatures, the alloy displays a better creep resistance and a longer creep lifetime. And the deformation features of the alloy during creep are that dislocations move in the γ matrix channels and shear into γ′ phase, the 〈1 1 0〉 super-dislocation shearing into γ′ phase may be decomposed on (1 1 1) planes to form the configuration of (1/3)〈1 1 2〉 super-Shockleys partials plus stacking faults, and some 〈1 1 0〉 super-dislocations shearing into γ′ phase can be cross-slipped from {1 1 1} planes to {1 0 0} planes to form K-W locking configuration of (1/2)〈1 1 0〉 + APB, which may hinder dislocations movement and restrain cross-slipping of dislocations. This is thought to be the main reason for the alloy having the better creep resistance at intermediate temperatures.