An enhanced TRIP material model for high martensite content evolution during deep drawing

Abstract

An enhanced Transformation Induced Plasticity (TRIP) material model based on the model from Hänsel was proposed in this paper to improve the stress-strain representation for high martensite contents for the metastable austenitic stainless steel 1.4301. Isothermal tensile tests were used as the data basis to rebuild the TRIP effect. The martensite content was measured in-situ during the experiments using a Feritscope. The transition from the Feritscope output to actual martensite content was described in detail, leading to higher martensite content results. Focus was placed on correcting the Villari effect, which indicated a dependence on the current yield strength. The proposed phenomenological model to correct the effect improved the correction, especially at high stresses. With the entire correction applied, over 80 % martensite was measured in an isothermal tensile test performed at 0 °C with no sign of saturation. The fitted enhanced material model achieved a very good agreement with the experimental martensite evolution and the stress-strain curve. The new definition of the prefactor and the exponent in the martensite formation rate model reduced the dependence of the optimization on the initial values. The introduced nonlinear mixture rule between the austenitic and the martensitic hardening was confirmed and improved the hardening representation by 35 %.