By means of measuring creep curves under the applied stress of 137 MPa at 1040 degrees C and observing the microstructure by SEM after the alloy was heat treated and crept, the microstructure evolution of [011] orientation single crystal nickel-base superalloy during tensile creep was investigated, and the effect factors of the evolution regularity was analyzed. Results show that, after full heat treatment, the microstructure of [011] oriented single crystal nickel-base superalloy consists of the cubic gamma' phase embedded coherently in the gamma matrix, regularly arranged along the < 100 > orientation. During tensile. creep, the cubic gamma' phase in the alloy is transformed into the strip-like rafted structure along the direction parallel to [001] orientation. In the action of the applied tensile stress along the [011] orientation, the extrusion stress is applied on the gamma' phase and (100) crystal plane of the cubic gamma' phase to generate the constricted strain of the lattice, which may exclude the Al and Ta atoms with bigger radius. Whereas, the expanding lattice strain appearing on the (001) crystal plane of the cubic gamma' phase may trap the Al and Ta atoms with bigger radius. Therefore, the cubic gamma' phase is directionally grown into the strip-like rafted structure along the [001] orientation. In the action of the applied stress, the change of the strain energy density in the different interfaces of the cubic gamma'/gamma phases is thought to be the driving force of the element diffusion and the directional coarsening of gamma' phase.
