Until recently, the dynamic strain ageing effect had been identified with "serrated flow" and, therefore, studied through the observation of serrations on the stress-strain curve. In this study, the dynamic strain ageing effect was observed through the strain rate sensitivity, i.e., the stress change due to the sudden change of strain rate during the deformation.
The new experimental methods attempted in this study are that the strain rate was changed at the same stress and strain on the cyclically stabilized stress-strain curve so that the work hardening effect could be eliminated, that after the strain rate change, the initial and the gradual stress changes were measured separately identifing the former with the viscous effect and the latter with the dynamic strain aging effect, and that the experiments were performed in relatively large strain rate range of $3.2 × 10^{-7}$ to $3.2 × 10^{-3}$ and temperature range of 20℃ to 800℃.
Among the substitutional alloys which are of our interests for the current study, 304 austenitic stainless steel was chosen as a test material because its dynamic strain ageing temperature and strain rate ranges suit best to our experimental facilities.
The main conclusions are that the dynamic strain ageing effect can be studied quantitatively and the strain rate change method is very effective for the purpose, and that, for 304 austenitic stainless steel, the dynamic strain ageing effect appears most strongly at the temperatures 300℃, 400℃, 500℃, and 600℃, for the strain rates $10^{-6}$, $10^{-5}$, $10^{-4}$, and $10^{-3}$, respectively.
