Tensile flow and work hardening behaviour of 9Cr–1Mo ferritic steel in the frame work of Voce relationship

Tensile stress–strain and work hardening behaviour of 9Cr–1Mo steel, containing three levels of silicon content (i.e., 0.24, 0.42 and 0.60 wt.%) have been examined in the temperature range 300–873 K in the framework of strain hardening law proposed by Voce. True stress–true plastic strain data for all test conditions were adequately described by Voce equation. The variations of work hardening parameters with temperature exhibited three different temperature regimes and displayed good correlations with the respective tensile properties of the steel. The variations of instantaneous work hardening rate with stress exhibited two-stage behaviour characterised by a rapid decrease in work hardening rate (transient stage) at low stresses followed by a gradual decrease (stage-III) at high stresses. Both work hardening parameters and instantaneous work hardening rate exhibited signatures of dynamic strain ageing at intermediate temperatures and dominance of dynamic recovery at high temperatures.

► Tensile σ–ɛ behaviour is adequately described by Voce strain hardening relation.
► Temperature dependence of work hardening parameters exhibited three distinct regimes.
► Voce parameters are well correlated with tensile properties at all temperatures.
► Instantaneous work hardening rate vs. stress exhibited two-stage behaviour.
► Influence of DSA and dynamic recovery are highlighted.