Simulation of the Austenite (γ) – Ferrite (α) transformation in steels within a finite element – level set numerical framework - Archive ouverte HAL Accéder directement au contenu
Communication Dans Un Congrès Année : 2018

Simulation of the Austenite (γ) – Ferrite (α) transformation in steels within a finite element – level set numerical framework

Résumé

The microstructure characteristics have significant impacts on the mechanical properties of the metallic materials. During the formingprocesses, phase transformations (PT) could occur to respond to the external thermomechanical loads (i.e. heat, mechanical works …)and minimize the free energy of the system.Among these phenomena, Austenite-Ferrite transformation plays an important role in metal forming of steels, as it’s closely relatedwith the other phase transitions occurring at lower temperatures (e.g. bainitic, martensitic transformations). The final state of themicrostructure (including phase fraction, morphology and grain size distribution of each phase) is hence indirectly influenced by theaustenite-ferrite transformation occurred in the upper range of temperature.The kinetic of the austenite-ferrite transformation involves some mechanisms: thermodynamic fluctuations (responsible of the phasenucleation) and energy minimizing (i.e. interface migration, solute diffusion).The complexity to model at the polycrystal scale the austenite-ferrite transformation generally comes from the difficulties to representnumerically the nucleation, to simulate the interfaces migration and the discontinuity of the solute diffusion through the interfaces.This discontinuity at the interfaces is classically treated in the well-known Phase Field (PF) approach by introducing an artificialdiffusive interface, implicitly described through the spatial distribution of a non-conserved order parameter evolving in time in orderto minimize a free energy describing the thermodynamics of the considered configuration.In this work, we introduce, in a finite element context, a new level set numerical framework. The diffusive interface in the phase fieldmodels is replaced by a sharp interface helping to remove purely numerical parameters inherent to classical phase field formulations.The need to build free energy is no longer necessary as the kinetics of the interface migration is simply described through a linearrelationship between the migration velocity and the thermodynamics driving forces. Thanks to the simplicity of the kinetics relations, we also aim to suggest a level set model corresponding to more complexconfigurations, where the interface mean curvature, as well as the jump of stored energy accross phase interfaces contribute to thephase interfaces migration in parallel with the phase transformation chemical potential driving force.

Domaines

Matériaux
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Dates et versions

hal-01973232 , version 1 (08-01-2019)

Identifiants

  • HAL Id : hal-01973232 , version 1

Citer

Chau Thuy Pham, Nathalie Bozzolo, Charbel Moussa, David Cardinaux, Aurore Montouchet, et al.. Simulation of the Austenite (γ) – Ferrite (α) transformation in steels within a finite element – level set numerical framework. Matériaux 2018, Nov 2018, Strasbourg, France. ⟨hal-01973232⟩
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