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 $\text{1}\text{3}\text{〈112〉}$ superpartials, but the $\text{1}\text{2}\text{〈110〉}$ screw components of them have moved away from the $\text{1}\text{6}\text{〈112〉}$ 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 $\text{1}\text{3}\text{〈112〉}$ superpartials with net slip vector 〈110〉 while the cores of the $\text{1}\text{3}\text{〈112〉}$ superpartials do not separate observably.