Dislocation dynamics in the oxide dispersion strengthened alloy INCOLOY MA956

In situ straining experiments in a high-voltage electron microscope have been performed on the oxide dispersion strengthened alloy INCOLOY MA 956 at room temperature and between 640 and 1010 degrees C to study the dynamic behaviour of dislocations. Macroscopic compression experiments including stress relaxation tests have been carried out between room temperature and 900 degrees C. The dynamic behaviour of dislocations, the flow stress and its strain rate sensitivity are discussed in the different temperature ranges in terms of long-range dislocation interactions, the Orowan mechanism, the model of the thermally activated detachment of dislocations from oxide particles, solution hardening and a diffusional point defect drag. It is concluded that the latter controls the thermally activated dislocation processes in a wide temperature range around about 700 degrees C. The detachment model may be active only above 900 degrees C. (C) 1999 Elsevier Science S.A. All rights reserved.