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°C to study the dynamic behaviour of dislocations. Macroscopic compression experiments including stress relaxation tests have been carried out between room temperature and 900°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°C. The detachment model may be active only above 900°C.