Dislocation Configurations in Single-Crystal Superalloys during High-Temperature Low-Stress Creep

Dislocation configurations in two single-crystal superalloys during high-temperature low-stress creep (1100 degrees C, 137 MP) were illustrated schematically with the use of transmission electron microscope (TEM). For an alloy with a small lattice misfit, the dislocations move in the combination of climbing and gliding processes. In the primary stage, the dislocations first move by slip in the gamma-matrix channels. When they reach the gamma' cuboids, they move by climb along the gamma' cuboid surfaces. In the secondary creep stage, dislocation reorientation in the (001) interfacial planes happens slowly, deviating from the deposition orientation of < 110 > to the misfit orientation of < 100 >. For an alloy with a large lattice misfit, the dislocations are able to move smoothly by cross slip in the horizontal gamma channels. The dislocation reorientation from the deposition orientation of < 110 > to the misfit orientation of < 100 > in the (001) interfacial planes can be completed in the primary creep stage.