A model for the strain rate dependent plasticity of a metastable austenitic stainless steel

• Strain rate history effects in metastable austenitic stainless steels are in this study shown to be notable.
• An internal variable based constitutive model that contains reasonable amount of parameters is developed.
• The effects of strain rate and adiabatic heating on material plasticity are separated by using strain rate jump experiments.
• Model is successfully verified with experimental data involving strong thermomechanical coupling.

A continuum material model is developed for the dynamic plastic deformation behavior of metastable austenitic stainless steel EN 1.4318-2B. An incremental approach in both experimental testing and in the model is used to distinguish between the direct effects of strain rate and the macroscopic adiabatic heating effects. In the model a set of evolution equations is integrated over the deformation path, which makes the model flexible in terms of changes in the strain rate and material temperature. The strain-induced phase transformation from austenite to α′-martensite is accounted for with evolution equations based on the Olson-Cohen transformation model. In order to describe the phase transformation accurately during dynamic loading, the original model is modified by adding instantaneous strain rate sensitivity to the α′-transformation rate. Comparison with experimental results shows that the model can be used to describe the strain rate and temperature dependent behavior of a metastable austenitic alloy with a reasonable number of material parameters. Finally, the model gives realistic results in a set of validation experiments.

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