Experimental investigation of the influence of the stress state on the mechanical stability of austenite in multiphase steels

Abstract
The transformation-induced plasticity (TRIP) effect, i.e. the mechanically activated martensitic transformation of metastable austenite, has been proven for some years to contribute very effective to the deformation process in a large variety of iron-based alloys. In order to enlighten the influence of the stress triaxiality on the kinetics of the mechanically-induced martensitic transformation in TRIP-assisted multiphase steels, several specimens presenting austenite with different mechanical stabilities were strained under different stress states (pure uniaxial tension, uniaxial tension of notched and DENT specimens and stretching). It is shown that the stress triaxiality has a large effect on the mechanical stability of austenite dispersed in a multiphase microstructure and consequently on the mechanical properties of the investigated steels.