Flow Curve Modelling of an Austenitic Stainless Steel at High Temperatures Starting from the One-Parameter Model of Strain Hardening

Giuliano Angella

doi:10.4028/www.scientific.net/MSF.706-709.1361

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Flow Curve Modelling of an Austenitic Stainless Steel at High Temperatures Starting from the One-Parameter Model of Strain Hardening
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Flow Curve Modelling of an Austenitic Stainless Steel at High Temperatures Starting from the One-Parameter Model of Strain Hardening

Abstract:

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 σ_V that defines the height of the flow curve, the critical strain ε_C that defines the velocity to achieve σ_V, and the stress σ_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 dσ/dε vs. the flow stress σ in order to obtain σ_V and ε_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 σ_V, σ_o, ε_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.