ICAMS / Interdisciplinary Centre for Advanced Materials Simulation

Plastic deformation by phase transformation: constitutive descriptions of TRIP steels

TRIP (TRansformation Induced Plasticity) steels count among the group of high-strength steels. They exhibit high strength and ductility at the same time. These characteristics can be traced back to the TRIP steel microstructure. The microstructure consists of retained austenite and bainite, which are embedded in a ferrite matrix. Retained austenite is metastable and can transform to martensite during straining. This project aims at developing a multi-scale model for TRIP steels based on crystal plasticity with the help of molecular statics and homogenization approaches.

Relaxed screw dislocation core in bcc iron.

Plastic deformation modelling of the ferrite matrix (bcc) is important, since there is no well accepted model in the literature. The deformation in bcc iron is dominated by glide of screw dislocations with non-planar dislocation cores. With the help of molecular studies a flow rule was embedded into the crystal plasticity approach, which takes the characteristic effects of bcc iron such as the strain rate and temperature dependence of the flow stress, the breakdown of Schmid’s law and the dependence of dislocation mobility on shear stress components that do not contribute to the mechanical driving force for dislocation glide into account. This flow rule is formulated for the [111] {110} slip system.

First results of the FEM simulation using the molecular static based crystal plasticity model show a qualitative accuracy compared to experimental data from the literature.

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