Abstract:The morphology evolution and creep behavior of g ¢ phase in [001] and [011] oriented specimens of a nickel-base single crystal superalloy during the tensile creep at 1253 K and 200 MPa were investigated. SEM and TEM observation shows that the direction coarsening of precipitates is highly dependent on the crystal orientation. In [001] orientation, the g ¢ phase transits from original cuboids to the raft-shape along the perpendicular direction to the tensile stress axis while in [011] orientation the g ¢ phase develops along the [010] and [100] and evolves into a raft with inclined 45° angle to the tensile stress axis. The strain rates for [001] and [011] orientations are almost equal at the earlier stage of creep. With the matrix channel broadening, the strain rate for [011] orientation increases gradually, while the creep strength decreases rapidly. Based on the evolutional rule of g ¢ phase and the creep curves, the anisotropic creep behavior is obvious at the later stage of steady-state and the tertiary creep stage