Advanced high strength steels, such as high manganese steels, show an extraordinary combination of strength and ductility. While this provides tremendous potential for many applications, these materials are not yet widely used in industry due to a number reasons. As simulation is nowadays an integral part of component layout e.g. in automotive industry, without suitable material models new materials will not be introduced into the production process.
We present a crystal plasticity formulation that includes both twinning and transformation as additional deformation mechanisms besides the conventional dislocation slip. The twinning model is a crystal plasticity adaption of an analytical model by Steinmetz et al. (2013) while the TRIP model is developed to model the ? (fcc) ? ? (hcp) ? ?’(bcc) transformation in austenitic steels.
This physics-based strain rate- and temperature sensitive model reflects the formation of dislocation structures, twinning and martensitic phase transformations using physically-based model parameters and ab initio derived thermodynamic quantities. Experimental data for a Fe-22Mn-0.6C steel, which exhibits both the TWIP effect and ? ? ? transformation as a function of stacking fault energy and loading conditions (strain rate, temperature), is used to validate the model. The combined model allows us to systematically study under which conditions either one or both mechanisms together can be triggered during deformation.
D. R. Steinmetz, T. Jäpel, B. Wietbrock, P. Eisenlohr, I. Gutierrez-Urrutia, A. Saeed-Akbari, T. Hickel, F. Roters, D. Raabe (2013): Revealing the strain-hardening behavior of twinning-induced plasticity steels: Theory, simulations, experiments, Acta Materialia 61: 494 - 510