Parametric study of multiphase TRIP steels undergoing cyclic loading

The behavior of multiphase steels assisted by transformation-induced plasticity (TRIP steels) undergoing low cycle, fully-reversed strain-controlled deformations is studied by means of numerical simulations based on micromechanical models. The ferritic phase is simulated using a single-crystal elasto-plasticity model for BCC crystals whereas the austenitic phase, which may transform into martensite, is simulated by a crystallographic phase transformation model coupled to a single-crystal elasto-plasticity model for FCC crystals. The influence of the TRIP mechanism on the overall behavior of the steel is investigated for selected variations of microstructural properties such as phase morphology, local carbon concentration in the austenite and austenitic grain size. The results of the simulations show a strong initial hardening associated to the martensitic transformation in accordance with experimental results. The simulations indicate an asymmetric hardening behavior under extension and contraction, particularly for large austenitic volume fractions and lower carbon concentrations.

Research highlights▸ This manuscript reports the study of TRIP steel behavior under cyclic deformation by means of cyrstallographically-based micro mechanical models. ▸ The effects of various microstructural properties on TRIP steel behavior under cyclic loading are analyzed. ▸ The martensitic phase transformation in TRIP-assisted steels promotes a strong hardening, particularly during the first cycles. ▸ The hardening of TRIP-assited steels during cyclic loading is more significant during compression, since less stress relaxation occurs.