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

Abstract

The dislocation structures of directionally solidified (DS) René 80 superalloy in γ′ phase during tensile deformation at 760°C and 850°C, and during creep deformation at 760°C under a stress of 618MPa 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 SISF separated 1 3 〈112〉 superpartials, but the 1 2 〈110〉 screw components of them have moved away from the 1 6 〈112〉 edge components on [111] plane, leaving a stress stabilized APB in its wake in tensile deformation. In contrast to 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 separate observably.