Study of the deformation mechanisms in a Fe–14% Cr ODS alloy

Praud, M.; Mompiou, Frédéric; Malaplate, J.; Caillard, D.; Garnier, J.; Steckmeyer, A.; Fournier, Benjamin

doi:10.1016/j.jnucmat.2011.10.046

Cited by 88 publications

(31 citation statements)

References 25 publications

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“…Atom probe tomography and transmission electron microscopy characterizations showed that the 14YWT NFA has a grain size of 200-400 nm and contains a high number density of Y-Ti-O NCs (1-2 nm in diameter) inhomogeneously distributed in the grains and along the grain boundaries 4,17 . As the alloy was made by hot-extrusion of mechanically alloyed powders, the 14YWT NFA tensile specimen exhibits a strong o1104 fibre texture, as seen from the neutron diffraction patterns and also consistent with the texture characterization in earlier works 18 .…”

Section: Resultssupporting

confidence: 86%

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

Stoica

Miller

et al. 2014

Nat Commun

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Nanostructured ferritic alloys are a new class of ultrafine-grained oxide dispersionstrengthened steels that have promising properties for service in extreme environments in future nuclear reactors. This is due to the remarkable stability of their complex microstructures containing numerous Y-Ti-O nanoclusters within grains and along grain boundaries. Although nanoclusters account primarily for the exceptional resistance to irradiation damage and high-temperature creep, little is known about the mechanical roles of the polycrystalline grains that constitute the ferritic matrix. Here we report an in situ mesoscale characterization of anisotropic responses of ultrafine ferrite grains to stresses using state-ofthe-art neutron diffraction. We show the experimental determination of single-crystal elastic constants for a 14YWT alloy, and reveal a strong temperature-dependent elastic anisotropy that leads to elastic softening and instability of the ferrite. We also demonstrate, from anisotropy-induced intergranular strains, that a deformation crossover exists from lowtemperature lattice hardening to high-temperature lattice softening in response to extensive plastic deformation.

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Section: Resultssupporting

confidence: 86%

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

Stoica

Miller

et al. 2014

Nat Commun

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“…The equivalent stress and strain rate are maximal close to the notch root, whereas for very low amounts of notch opening (as in the present work), the maximum principal stress and maximum stress triaxiality are located close to the specimen center, together with a very low strain rate. In this material family, it has been shown that a decrease in tensile strain rate leads to an increase in intergranular damage development [Praud et al, 2012], which agrees with the more extended damage development during creep tests than in tensile tests, also noticed in the present work. According to the loading rate of NT specimens, three cases could be encountered:…”

Section: Toward a Macroscopic Criterion For Intergranular Fracturesupporting

confidence: 92%

“…A maximum in the elongation vs. temperature curves, already known for 14Cr ODS steels [Praud et al, 2012], was observed around 600°C for tensile tests along AD, but not along RD. The reduction of area at fracture was low (around 20%) for tests along RD and rather independent of the test temperature (Fig.…”

Section: Uniaxial Tension Behaviorsupporting

confidence: 50%

Anisotropic intergranular damage development and fracture in a 14Cr ferritic ODS steel under high-temperature tension and creep

Salmon-Legagneur

Vincent

Garnier

et al. 2018

Materials Science and Engineering: A

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This work addresses damage mechanisms at high temperature of a hot extruded 14Cr oxide dispersion strengthened steel rod, in particular, anisotropy induced by its strong morphological and crystallographic texture. Under uniaxial tension, intergranular damage and unstable fracture increased with test temperature; they appeared much easier along the rod axis than perpendicular to it. Creep fracture of smooth specimens involved crack initiation from the side surfaces and intergranular crack propagation, accompanied by intergranular damage.In order to get rid of fracture surface oxidation by the air environment, a methodology promoting crack nucleation from inside the specimen was built. From tensile and creep tests on notched specimens the fracture initiation location and fracture stability were first mapped as a function of test temperature, maximal stress triaxiality and loading direction. Then, for the first time to the authors' knowledge, interrupted tests on notched tensile and creep specimens, followed by low-temperature fracture allowed revealing fracture surfaces formed at high temperature, but unconnected to the external environment. Intergranular fracture and grain boundary grooving were evidenced there, together with strong chemical reactivity at the surface of internal cavities during damage development at high temperature.

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“…A peak of ductility is observed at 1200°C and 5 s À1 . The ductility increase with strain rate was already reported by other studies through tensile tests at temperatures up to 750°C and strain rates between 10 À5 and 5 Á 10 À2 s À1 [9,17]. However, in the torsion conditions, the rising temperature induced by plastic dissipation, especially at high strain rates, may explains the increase ductility observed in Fig.…”

supporting

confidence: 73%

Microstructural characterizations of 14Cr ODS ferritic steels subjected to hot torsion

Karch

Sornin

Barcelo

et al. 2015

Journal of Nuclear Materials

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Study of the deformation mechanisms in a Fe–14% Cr ODS alloy

Cited by 88 publications

References 25 publications

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

Temperature-dependent elastic anisotropy and mesoscale deformation in a nanostructured ferritic alloy

Anisotropic intergranular damage development and fracture in a 14Cr ferritic ODS steel under high-temperature tension and creep

Microstructural characterizations of 14Cr ODS ferritic steels subjected to hot torsion

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