Interface dislocations in superalloy single crystals

The overall. stress state in gamma-channels of gamma/gamma'-microstructures has three components: misfit stresses (due to gamma/gamma'-misfit), disloc ation stress fields and the external stress. In the present study glide and climb forces on gamma-channel dislocations (from one slip system a(o)/2[01 (1) over bar](111)) are studied calculating Peach-Koehler forces for gamma /gamma'-interface dislocations exposed to the overall stress state. A therm o-elastic finite element calculation of misfit stresses is performed and th e results are used as one input into a simplified discrete dislocation mode l (DDM). The influence of gamma'-volume fraction and dislocation density in the gamma-channels is explicitly considered. The calculations were motivat ed by previous mechanical and microstructural investigations in which eleme ntary dislocation processes were identified by transmission electron micros cropy as part of the mechanism of high temperature and low stress creep. Th e results help to interpret phenomenological concepts (like build up of bac k stress) and rationalize microstructural findings (like dislocation networ k spacings). (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.