Skip to Main content Skip to Navigation
Theses

Aciers bainitiques sans carbure : caractérisations microstructurale multi-échelle et in situ de la transformation austénite-bainite et relations entre microstructure et comportement mécanique

Abstract : Carbide-free bainitic steels are part of the 3rd generation of advanced high strength steels, which exhibit high yield strength and an excellent compromise between tensile strength and ductility. These ground ? breaking properties are achieved thanks to the characteristics of their microstructure which is constituted of different phases (bainite, austenite and martensite) organized in a specific way (typical bainitic colonies and residual islands). However, relationships between microstructural features and mechanical properties are yet to be thoroughly established. In the frame of this PhD, we investigated these relationships in carbide-free bainitic steels elaborated by an austempering process. Various means of characterization were used in situ and post mortem to analyze qualitatively and quantitatively microstructures elaborated by the decomposition of the austenite in isothermal conditions. The influence of the austempering temperature and the carbon content on the microstructures has been highlighted. Moreover, austempering under Ms allowed elaborating a microstructure constituted of tempered martensite, bainitic ferrite and residual austenite. Tensile and shear tests were performed in order to evaluate their mechanical properties and to estimate the kinematical and isotropic contributions of the workhardening. Results were analyzed in the light of the microstructural characterizations and the effects of some microstructural features have been highlighted. The mechanical behavior of the bainite elaborated under Ms was estimated by a micromechanical approach based on a law of mixtures between the tempered martensite and the compound made of bainitic ferrite and residual austenite
Document type :
Theses
Complete list of metadatas

Cited literature [48 references]  Display  Hide  Download

https://hal.univ-lorraine.fr/tel-01749071
Contributor : Thèses Ul <>
Submitted on : Thursday, March 29, 2018 - 12:00:21 PM
Last modification on : Friday, July 17, 2020 - 2:58:14 PM
Long-term archiving on: : Friday, September 14, 2018 - 7:57:49 PM

File

Hell.Jean_Christophe.SMZ1131.p...
Files produced by the author(s)

Identifiers

  • HAL Id : tel-01749071, version 1

Citation

Jean-Christophe Hell. Aciers bainitiques sans carbure : caractérisations microstructurale multi-échelle et in situ de la transformation austénite-bainite et relations entre microstructure et comportement mécanique. Autre. Université Paul Verlaine - Metz, 2011. Français. ⟨NNT : 2011METZ031S⟩. ⟨tel-01749071⟩

Share

Metrics

Record views

87

Files downloads

1384