Transformation-induced plasticity in multiphase steels subjected to thermomechanical loading.

Denny Tjahjanto (1) , Sergio Turteltaub (1) , Akke S.J. Suiker (1) , Sybrand van Der Zwaag (1)

1 Faculty of Aerospace Engineering [Delft]

The behavior of transformation-induced plasticity steels subjected to combined thermomechanical loading is studied at the microscale by means of numerical simulations. The microstructure is composed of an austenitic phase that may deform plastically and/or transform into martensite, and a ferritic phase that may deform plastically. The micromechanical models capturing these effects are derived from a thermodynamical framework, which has been extended from previous works in order to adequately account for the thermal contributions to the kinematics and the Helmholtz energy. The models are used in numerical simulations on a polycrystalline sample composed of an aggregate of multiple austenitic and ferritic grains of various orientations. The thermomechanical response of the sample is studied under (i) isothermal straining at different temperatures above the martensitic start temperature, and under (ii) different paths of straining and cooling to temperatures below the martensitic start temperature. The first type of analysis shows that at lower temperatures the transformation mechanism is more dominant than the plasticity mechanism, whereas the converse occurs at higher temperatures. The second type of analysis illustrates that the transformation rate under straining is higher when performed on an pre-cooled sample but, in contrast, the transformation rate under cooling is lower when carried out on a pre-strained sample. The results of this analysis indicate that, for optimizing the formability of this class of steels, it is recommendable to make a judicious choice regarding the thermomechanical loading parameters during manufacturing processes.

Mots clés: Physical Sciences

Denny Tjahjanto, Sergio Turteltaub, Akke S.J. Suiker, Sybrand van Der Zwaag. Transformation-induced plasticity in multiphase steels subjected to thermomechanical loading.. Philosophical Magazine, 2009, 88 (28-29), pp.3369-3387. ⟨10.1080/14786430802438150⟩. ⟨hal-00513963⟩