Hot deformation behavior of n-ODS-18Cr steel

In the present work, nano oxide dispersion strengthened (ODS) steel was prepared by high energy ball milling of the elemental powders, followed by canning and upset forging. The chemical composition of the material used in this study is Fe-17.8Cr-2.33W-0.23Ti-0.35Y2O3. Isothermal compression tests were carried out on upset forged ODS-18Cr steel samples over a range of temperatures (1273 to 1423 K) and strain rates (10-2 s-1 to 10 s-1) utilizing Gleeble-3800 machine. Transmission electron microscopy and electron back scattered diffraction were carried out on the deformed samples to evaluate the grain size and to identify dynamic recrystallized grains. The true stress- true strain data obtained from compression tests at different strain rates were also utilized to estimate and rationalize the activation energy for deformation and the stress exponent. The obtained deformation mechanism parameters are greater than those for the non-ODS steels, which is attributed to the threshold stress generated due to dislocation/particle interaction. Sellars-Tegart equation was used to predict the peak flow stress and the predicted results were comparable to the experimental results.