Étude des mécanismes de déformation et d’adoucissement dynamique des aciers ferritiques Fe-Cr au cours de la déformation à chaud

Lombry, R.; Rossard, C.; Thomas, Beth

doi:10.1051/metal/198178120975

Cited by 32 publications

(6 citation statements)

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“…The present results, as well as the above studies of the as-cast ferritic steels, show that there is no DRX in the ferrite as some claim [69][70][71]. Evidence in the literature reports the production of intragrain high misorientation boundaries generally at much higher strains than the present ones [10,[21][22][23]50]. This has been explained primarily by the formation of transition boundaries between deformation bands produced by different slip systems, developing locally misoriented areas and also by the theory of geometric DRX [16,[19][20][21][22][23].…”

Section: Microstructural Behavioursupporting

confidence: 52%

“…The stress/strain characteristics of 2304 and 2205 duplex steels studied in the present work ( Figure 1) are much different from the flow curves of homogenized ferritic steels known from the literature [10][11][12][13][14][15][53][54][55][56]. At low temperatures, they are truncated by failure at much lower strains.…”

Section: Mechanical Behaviourmentioning

confidence: 84%

“…Ferrite exhibits a lower flow stress than the g phase and exceptional fracture strain, e f , both in pure Fe up to 910 °C and in Fe-Cr or Fe-Si alloys up to much higher temperatures. These properties arise from the ability of ferrite to undergo dynamic recovery (DRV) which results in the annihilation of a high fraction of dislocations generated during the deformation [9][10][11][12][13][14][15][16][17]. The remaining dislocations polygonize into subgrains which have larger diameters, lower internal dislocation content and walls of simpler arrays as the temperature rises or strain rate declines.…”

Section: Introductionmentioning

confidence: 99%

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Hot Workability of 2304 and 2205 Duplex Stainless Steels

Evangelìsta¹,

McQueen²,

Niewczas³

et al. 2004

Canadian Metallurgical Quarterly

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The duplex stainless steels 2304 and 2205 were subjected to torsion testing over the range of temperatures from 1000 to 1200 °C and strain rates from 0.1 to 5 s -1 to characterize their hot working behaviour. The flow curves exhibit a peak followed by a decline towards a steady state that is attained at high temperatures and low strain rates. The peak stresses are fitted to a sinh-Arrhenius constitutive equation with activation energies of 536 and 406 kJ/mol, respectively. The optical microstructure shows elongated austenite regions in a ferrite matrix that increase in volume fraction with a rising temperature. The austenite phase becomes more elongated as the fracture strain rises indicating that both phases codeform in the temperature regime studied.During hot deformation, the ferrite effectively undergoes dynamic recovery, thus its substructure consists of well polygonized subgrains. In contrast, dynamic restoration processes are much suppressed in the austenite phase. The austenite substructure contains dense irregular dislocation networks and the dynamic recrystallization is observed only at very high temperatures. The hot ductility of the steels is limited by the cracking at the ferrite/austenite interphase boundaries; however, it improves as the temperature rises and the strain rate declines reaching maximum true strains of about 1.2 and 3, respectively. Present results indicate that the hot workability of 2304 and 2205 duplex stainless steels can be improved modestly by multistage testing. This is attributed to the static restoration processes (static recovery of ferrite and static recrystallization of austenite) which reduce internal stress concentrations but can not inhibit interphase boundaries from nucleating the cracks.Résumé -On a soumis les aciers inoxydables duplex 2304 et 2205 à des essais de torsion dans la gamme de températures de 1000 à 1200 °C et à des vitesses de déformation de 0.1 à 5 s -1 afin de caractériser leur comportement de travail à chaud. Les courbes d'écoulement exhibent un pic suivi par un déclin vers une asymptote qui est atteinte à températures élevées et à basses vitesses de déformation. On ajuste les pics de contrainte à une équation constitutive de sinh-d'Arrhénius avec des énergies d'activation de 536 et 406 kJ/mol, respectivement. La microstructure optique montre des régions allongées d'austénite, dans une matrice de ferrite, dont la fraction volumique augmente avec une élévation de la température. La phase d'austénite s'allonge à mesure que l'effort de rupture s'élève, indiquant que les deux phases se co-déforment dans le régime de température étudié.Lors de la déformation à chaud, la ferrite subit effectivement une récupération dynamique, donc sa sous-structure consiste en sous-grains polygonaux bien formés. Par contraste, les procédés de restauration dynamique sont plutôt supprimés dans la phase d'austénite. La sous-structure de l'austénite contient des réseaux denses et irréguliers de dislocations et la recristallisation dynamique est observée seulement à des températu...

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Section: Microstructural Behavioursupporting

confidence: 52%

Section: Mechanical Behaviourmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Hot Workability of 2304 and 2205 Duplex Stainless Steels

Evangelìsta¹,

McQueen²,

Niewczas³

et al. 2004

Canadian Metallurgical Quarterly

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“…The GB become strongly serrated and thus indistinguishable from SGB; consequently a GRX-like mechanism occurs, although it has not been thoroughly investigated [190]. In distinction, at strains near 4, Lombry and Rossard [285] observed the formation of a network of boundaries with q : 12°enclosing regions of low q subgrains and being distinct from the carbide decorated GB. These regions are smaller in scale than in deformation bands in Al, possibly because of the different slip symmetry in the body centered cubic crystals.…”

Section: Ferritic Steelsmentioning

confidence: 99%

Current issues in recrystallization: a review

Doherty¹,

Hughes²,

Humphreys³

et al. 1997

Materials Science and Engineering: A

2,063

623

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The current understanding of the fundamentals of recrystallization is summarized. This includes understanding the as-deformed state. Several aspects of recrystallization are described: nucleation and growth, the development of misorientation during deformation, continuous, dynamic, and geometric dynamic recrystallization, particle effects, and texture. This article is authored by the leading experts in these areas. The subjects are discussed individually and recommendations for further study are listed in the final section. © 1997 Elsevier Science S.A.

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“…Compared to the high temperature austenite form of the ferritic steels [22], the fcc structure of ZrC also displays a high multiplicity of glide systems. At low temperature, slip occurs only on the {110} 〈110〉 system, with 2 independent slip systems.…”

Section: Microstructure Of Sintered Samplesmentioning

confidence: 98%