Dislocation structure due to high temperature deformation in the γ′ phase of a nickel-based superalloy

Abstract

The dislocation structures of directionally solidified René 80 superalloy in the γ′ phase during tensile deformation at 760 and 850°C, and during creep deformation at 760°C under a stress of 618 MPa have been studied by transmission electron microscopy. It has been shown by an extensive analysis of the dislocations bounding a superlattice stacking fault that γ′ shearing occurs by viscous slip of pairs of 1 3 〈112〉 superpartials separated by superlattice intrinsic stacking faults (SISFs) but the 1 2 〈110〉 screw components of these have moved away from the 1 6 〈112〉 edge components on the [111] plane, leaving a stress-stabilized antiphase boundary in its wake in tensile deformation. In contrast with the tensile glide mechanism, in creep deformation γ′ shearing occurs by viscous slip of pairs of SISF-separated 1 3 〈112〉 superpartials with net slip vector 〈110〉 while the cores of the 1 3 〈112〉 superpartials do not appear to be separated.