Superposition of external and internal stress components in gamma/gamma '-microstructures and their effect on gamma-channel dislocations

Glide and climb forces on gamma-channel dislocations in gamma/gamma'-micros tructures are calculated considering a simplified scenario involving discre te dislocations. The influence of (i) misfit stresses, (ii) volume fraction of gamma'-particles, (iii) the density of channel dislocations and (iv) th e external stress is considered. In the approach taken in this study we sup erimpose misfit stresses from thermo-elastic FEM-calculations with applied stresses and with stresses caused by discrete channel dislocations. The cal culations are based on previous mechanical and microstructural results wher e a number of dislocation reactions were observed using TEM and identified as relevant microstructural elements of the overall mechanism of high tempe rature and low stress creep. Preliminary results show that in a realistic m icrostructural scenario there is a limit to the number of dislocations whic h can enter a gamma-channel by glide (in the absence of recovery processes) . This number depends on gamma'-volume fraction and on gamma/gamma'-misfit. Moreover it was found that glide and climb forces depend on the position o f the dislocation segment in the channel and that there is a general tenden cy to push dislocations out of the channels.