Influence of thermomechanical processing and tempering temperature on tensile flow and work hardening behaviour of India specific reduced activation ferritic martensitic steel

Abstract

In the present work, an indetailed investigation has been carried out on the effect of thermomechanical treatment (TMT) and tempering temperature on microstructural features, tensile flow characteristics and work hardening behaviour of the India specific reduced activation ferritic martensitic (INRAFM) steel. The flow and work hardening characteristics of the studied steel are described by using the Voce constitutive equation and Kocks- Mecking (K-M) approach respectively in the temperature range of 300–873 K. The steel subjected to TMT and tempering for 90 min at 1033 K shows a refined martensitic lath width, finer size (Cr/W/Fe)23C6 and (V/Ta) (C/N) precipitates with an increment in number density. Furthermore, increase in tempering temperature coarsened the refined structural features. Voce equation closely fits the flow curves at 823 K and 873 K, but shows a slight deviation at temperatures below 773 K. The parameters derived from Voce equation are fairly in good correaltion with the experimental values. The strain hardening rate (θ) vs. true stress (σ) plots portrayed stage-I and stage-III work hardening stages and their corresponding phenomena were discussed. In addition, the effect of TMT and tempering treatment on the work hardening parameters obtained from K-M approach and inter-barrier spacing of the steel were also presented in this study. The work hardening characteristics of the steel signifcantly improved upon TMT due to refinement in microstructural features. The flow stress and work hardening parameters decreases with raise in test temperature due to the dominant effect of dynamic recovery.