It has been established that dislocation creep results in a threshold stress for oxide dispersion strengthened (ODS) alloys. However, the physical origin of this stress is still a matter of debate. Microstructural observations will be presented of the ODS alloy Inconel MA 754, showing dislocations pinned on the departure side of the dispersoids. This departure side pinning is proposed to occur because dislocation/particle association leads to a lower energy configuration relative to the case when the dislocation and dispersoid are not in contact. It will be shown that the observed threshold stress value can be that of the applied stress necessary to overcome departure side pinning. In addition, the concept of an effective stress for creep is shown to explain the extremely large stress exponents generally observed for ODS alloys.
