Microstructure evolution and deformation mechanism of a [111]-oriented nickel-based single-crystal superalloy during high-temperature creep

Abstract

Through creep measurement and microstructure observation, the microstructure evolution and deformation mechanism of a [111]-oriented nickel-based single-crystal superalloy at 980 °C/186 MPa were studied. The results show that the [111]-oriented single-crystal superalloy after full heat treatment featured cubic γ' phases coherently embedded in the γ phases and regularly arranged along the <100> direction. During the creep, the cubic γ' phases were interconnected, phase thickening and coarsening occurred, and the phase transformed into a lamellar rafted structure that grew staggered in three-dimensional space. The deformation characteristics of the [111]-oriented nickel-based single-crystal superalloy during creep under experimental conditions were that the dislocations slipped, propagated, and climbed over the γ' phases in the matrix, and then cut into the γ' phase and cross-slipped from the {111} plane to the {100} plane to form Kear–Wilsdorf (K–W) locks. Finally, the dislocations cut the γ' phase in the form of dislocation pairs, causing the γ' phase to lose its creep resistance, resulting in creep fracture.