Thesis Defense – Louis Hennocque – November 14, 2024

Louis HENNOCQUE will defend his thesis titled “Recrystallization in Ferritic Stainless Steels: Experimental Approach and Modeling” on November 14, 2024, at 10 AM in Amphitheater F1 of the main building of École des Mines de Saint-Étienne (158 cours Fauriel 42100 Saint-Étienne).

The defense will be followed by the traditional thesis reception, to which participants are cordially invited.

Jury

• Roland Logé, Professor, EPFL, Examiner
• Brigitte Bacroix, CNRS Research Director, LSPM, Examiner
• Maurine Montagnat, CNRS Research Director, IGE Grenoble, Reviewer
• Michel Perez, Professor, MATEIS-INSA Lyon, Reviewer
• Guillaume Kermouche, Professor, Mines Saint-Étienne, Thesis Supervisor
• Laurence Latu-Romain, Professor, Univ. Grenoble Alpes, SIMaP, Co-supervisor
• Julien Favre, Senior Lecturer, LGF, Co-advisor
• Nicolas Meyer, Research Engineer, Ugitech, Co-advisor
• David Piot, Research Officer, LGF, Invited Member
• Thomas Sourisseau, Research Engineer, Ugitech, Invited Member

Abstract

Mastering microstructural evolutions during hot rolling of ferritic stainless steels remains a major challenge for optimizing final mechanical properties. This study aims to understand and model the plasticity, restoration, and recrystallization mechanisms that govern these evolutions. The main objective is to elucidate how process parameters influence the final microstructure and, consequently, the material properties.

An approach combining experimentation and theoretical modeling was adopted. Elementary thermomechanical cycles, performed by hot compression and torsion, allowed for controlled simulation of industrial conditions. A thorough rheological and microstructural analysis in dynamic and post-dynamic regimes was conducted, leading to the proposal of a new nucleation criterion. This criterion accurately predicts the nucleation frequency and germ size, thus offering a better understanding of recrystallization phenomena.

An innovative recrystallization model was developed, coupling continuous dynamic recrystallization (CDRX) mechanisms with the proposed new nucleation criterion. This model offers a more accurate representation of the microstructural processes at play during hot rolling. The results of this study significantly contribute to the optimization of industrial hot rolling processes for ferritic stainless steels, opening promising perspectives for improving the quality and performance of final products.

Keywords

Ferritic stainless steels, hot rolling, microstructural evolution, recrystallization, modeling, rheology, nucleation.