Texture evolution analysis in oxide dispersion strengthened ferritic steel transformed by a tube pilgering process

E. Vakhitova (1) , D. Sornin (1) , Manuel François (2)

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)
2 LASMIS - Laboratoire des Systèmes Mécaniques et d'Ingénierie Simultanée

Ferritic Oxide Dispersion Strengthened (ODS) steels are investigated as potential materials for cladding tubes of advanced Sodium Fast Reactors. Pilgering process is used to cold-form the ODS seamless tubes with a large cross-section reduction in a double processing step. To estimate the influence of process parameters on the material, a microstructure analysis is carried out by Electron Backscattering Diffraction (EBSD) and X-ray Diffraction (XRD) methods. These data were used to obtain information about crystallographic texture, misorientation distributions, grain size, low and high angle boundary fractions and Schmid factor. Pilgered samples show a high texture formation with the well-known $\alpha$-fiber preferential orientation along the rolling direction. During the heat treatment process, grain morphology is restored from elongated grains to the almost equiaxed ones, while the texture presents unexpected increasing of fiber intensity. The remarkable temperature stability of this fiber is assumed to be linked to the texture memory of crystallographic structure during severe cold rolling process. The special attention was paid to the slip activation mechanism during plastic deformation applied by pilgering process. To predict this specific texture formation, modeling investigation of tube deformation process is performed using a polycrystalline self-consistent visco-plastic (VPSC) code. Pilgering forming is modeled by a sequence of deformation path considering the initial grain orientation sets obtained from EBSD maps results. It assumes a simple cyclic loading paths estimating the experimental loading associated to the pilgering process. The effect of initial and induced texture on the mechanical hardening is estimated and a set of hardening parameters is identified. Finally, the results of the traction tests along the rolling and transverse directions are compared to the numerical simulations.

Keywords: ODS steel; cold rolling process; residual stresses; texture; visco-plastic self-consistent model (VPSC)

Domains: Nuclear Experiment [nucl-ex]; Nuclear Theory [nucl-th]

E. Vakhitova, D. Sornin, Manuel François. Texture evolution analysis in oxide dispersion strengthened ferritic steel transformed by a tube pilgering process. 18th International Conference on Textures of Materials (ICOTOM-18), Nov 2017, Saint George, United States. ⟨cea-02437072⟩