Tensile flow and work hardening behavior of reduced activation ferritic martensitic steel subjected to thermo-mechanical treatment

The effect of thermo-mechanical processing of 9Cr-1W-TaV reduced activation ferritic martensitic (RAFM) steel on tensile flow and work hardening behavior has been studied and compared with RAFM steel in Normalized and Tempered (N + T) condition. Upon thermo-mechanical treatment (TMT) processing, the tempered martensitic structure of the steel underwent refinement in terms of lath size and precipitates with an increase in dislocation density. Considerable improvement in tensile flow properties without appreciable loss of ductility is observed at test temperatures 300–923 K and at a strain rate of 3 × 10−4 s−1. The plots of work hardening rate (θ) vs. stress (σ) revealed transient and stage-III stages of work hardening for both TMT and N + T steels. However, the TMT processing increased the work hardening of the steel, as manifested by the shift in θ vs. σ plots to higher stresses at all the temperatures and an increase in the fraction of transient stage of θ vs. σ plot up to a temperature of 773 K. Further, an increase in stress to onset of stage-III and the decrease in rate of dynamic recovery (Stage-III) have been observed for TMT steel, in comparison to the steel in N + T condition. This is attributed to the decrease in inter-barrier spacing of the obstacles, in TMT steel, measured analytically. The above-mentioned observations substantiated the beneficial effect of TMT processing on tensile flow and work hardening of the RAFM steel. •TMT induced refinement of M23C6/MX particles & martensite lath width in RAFM steel.•TMT enhanced tensile strength properties without compromising the ductility.•Work hardening rate of TMT RAFM steel is higher than that of N + T RAFM steel.•TMT steel own low inter-barrier spacing & high stress to onset of dynamic recovery.