Berrahmoune, Mohamed Reda (2006) Martensitic transformation and delayed cracking phenomenon in the 301LN unstable austenitic steel. PhD thesis Mécanique et Matériaux, ENSAM, ENSAM 2006ENAM0041 p.186.
Abstract
The automotive industry requires increasingly steels with good combination of high strength and good formability. Unstable austenitic stainless steels combine these properties, making them very attractive. However, under specific conditions in the field of drawing, delayed cracking phenomenon can appears in this kind of steels. The aim of this work is the study of the delayed cracking phenomenon related to the martensitic transformation in the 301LN unstable austenitic stainless steel. For that, we divided this work into two parts: Thermomechanical Behaviour : This part deals with the characterization of martensitic transformation after uniaxial loading under different of temperature and strain rate conditions. The stress distribution between the
phases, the martensitic transformation kinetics, and the evolution of crystallographic texture are determined by X
Rays Diffraction (XRD) under uniaxial in-situ tensile tests.
Multi-scales analysis of the delayed cracking phenomenon : study of the delayed cracking phenomenon are done on deep drawing cups. The identification of microstructural parameters which are responsible of crack initiation is realised by Scanning Electronic Microscopy (SEM). For different conditions of drawing, both, macroscopic residual stress and residual stress distribution between phases are determined and associated to the martensite content in the cups. Numerical simulations of deep drawing process are realised by implementation of two martensitic transformation models in the unstable austenitic steels. Numerical results are compared to our experimental results. We establish a relation between stress state in the martensite, volume fraction of formed martensite, and the delayed cracking phenomenon.
| Item Type: | PhD Thesis (PhD) |
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| Thesis Supervisor: | Inal, Karim |
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| Date: | 06 December 2006 |
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| Board of examiners: | Schmitt, Jean Hubert and Denis, Sabine and Pilvin, Philippe and Berveiller, Sophie and Inal, Karim and Patoor, Etienne and Glez, Jean Christophe |
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| Ecole Doctorale: | ED 432 ECOLE DOCTORALE SCIENCES DES METIERS DE L'INGENIEUR |
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| Discipline: | Mécanique et Matériaux |
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| Collection (Fonds): | ENSAM |
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| Institution: | ENSAM |
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| Department: | ENSAM |
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| Subjects: | 4. Materials Science, Mechanics and Mechanical Engineering |
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| Uncontrolled Keywords: | Austenitic stainless steels, Martensitic transformation, Delayed cracking, Residual stress state, X Rays diffraction, Aciers inoxydables austénitiques, Transformation martensitique, Rupture différée, état de contraintes résiduelles, diffraction des rayons X |
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