The effect of lattice misfit on the dislocation motion in superalloys during high-temperature low-stress creep

The development of dislocation configurations in two single-crystal superalloys during high-temperature low-stress creep (1100 degrees C, 137 MPa) was investigated with the use of transmission electron microscopy. Detailed analysis showed that the lattice misfit has an important influence on the dislocation movement. For an alloy with a large negative lattice misfit, the dislocations are able to move smoothly by cross-slip in the horizontal gamma channels. During subsequent formation Of gamma/gamma' rafted structure, the dislocations on the surface of gamma' cuboids rapidly re-orientate themselves from < 110 > to < 100 > direction and form a complete network. For an alloy with a small lattice misfit, the dislocations move by the combination of climbing and gliding processes, and the resultant gamma/gamma' interfacial dislocation network is incomplete. A good explanation of the creep curves is obtained from these differences in the microstructures. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.