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Keynote Lecture

A review of recent developments for parent microtexture reconstruction with Merengue 2 Application to the analysis of the deformation substructure of austenite and its influence on microstructure inheritance in low carbon steels

Wednesday (28.09.2016)
14:45 - 15:15
Part of:

Recent developments in MERENGUE 2 [1] allow significant improvements in the reconstruction of parent microstructure (i.e austenite) from transformation products (i.e. martensite, bainite) measured after phase transformation. Two main hypotheses are required in order to be able to apply such a technique: The occurrence of a phase transformation with an orientation relation and the transformed product must form in its parent grain. Following our recent improvements, four significant improvement are detailed:

- The orientation relationship may be measured faster and with a higher reliability thereby allowing for lower tolerance angles in the search of the unique parent.

- Upper bainite microstructures contain many low angle misorientations (blocks) which are better discriminated thanks to an optimized algorithm for crystallographic domain reconstruction (ALGrId [2]) thereby improving the reconstruction of parent boundaries.

- Sigma-3 twins boundaries are very difficult to reconstruct correctly since the same 6 variants may be formed on each side of a twin boundary. To improve their reconstruction an automated method which uses the twin plane trace is applied during the reconstruction process.

- Most reconstruction methods work under the hypothesis that the parent orientation is unique. However, this hypothesis does not apply in the case of a deformed parent microstructure. To account for the orientation gradient a new approach was developed.

Our crystallographic reconstruction tool MERENGUE 2 is finally successfully applied to evaluate the deformation substructure of a low carbon steel (C0.06-Mn2.4-Si0.3 (w%)) deformed by compression at 800°C up to strains of 0.6 [3]. We analyzed how this substructure influences on the nature of transformation products (type of product : granular bainite, lath-like bainite/martensite, OR, variant selection).

[1] Germain L, Mémoire d’Habilitation à Diriger des Recherche. Université de Lorraine, 2014.

[2] Germain L, Kratsch D, Salib M, Gey N. Mater Charact 2014;98:66.

[3] Boucard E. PhD Thesis, Université de Lorraine, 2014.


Dr. Lionel Germain
University of Lorraine
Additional Authors:
  • Dr. Nathalie Gey
    Université de Lorraine
  • Dr. Elodie Boucard
    Université de Lorraine
  • Dr. Sebastian Cobo
    ArcelorMittal Maizières
  • Prof. Dr. Michel Humbert
    Université de Lorraine