Flow curve modelling of an austenitic stainless steel at high temperatures starting from the one-parameter model of strain hardening

The flow curves of an austenitic stainless steel deformed at temperatures 700-1000°C with strain rates 10 -5-10 -2 s -1 were modelled with the Voce equation. The parameters needed to draw the Voce equation, are the saturation stress ? V that defines the height of the flow curve, the critical strain ?C that defines the velocity to achieve ? V, and the stress ? o, namely the back-extrapolated flow stress to zero strain. A modified strain hardening analysis based on the one-parameter model was used to analyze the strain hardening rate d?/d?vs. the flow stress ? in order to obtain ? V and ? C. The modified approach was based on the assumption that the dislocation multiplication component of strain hardening was temperature and strain rate dependent through the thermal activation term s of flow stress. A parameter s' proportional to s was obtained from the strain hardening analysis and a relationship between s' and temperature and strain rate was found. Relationships between ? V, ? o, ? C and s' were finally established and at this stage the Voce equation could reproduce the experimental flow curves at any imposed deformation conditions of temperature and strain rate.