Investigation of Phase Transformations in High-Alloy Austenitic TRIP Steel Under High Pressure (up to 18 GPa) by In Situ Synchrotron X-ray Diffraction and Scanning Electron Microscopy

Ackermann, S.; Martin, Stefan; Schwarz, Marcus; Schimpf, Christian; Kulawinski, Dirk; Lathe, C.; Henkel, Sebastian; Rafaja, David; Biermann, Horst; Weidner, Anja

doi:10.1007/s11661-015-3082-2

Cited by 29 publications

(15 citation statements)

References 84 publications

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“…The first part of the curves was due to the interaction of the (partial) dislocations and the grain boundaries. This represents the normal behavior of dislocations observed in fcc alloys . Consequently, the small grain size from the FAST TRIP steel resulted in the highest strain hardening.…”

Section: Resultsmentioning

confidence: 79%

“…In general, the deformation‐induced ϵ‐martensite in the high‐alloy TRIP steel investigated was not considered as a phase in terms of thermodynamics. By means of in‐situ synchrotron experiments under isostatic pressure, Ackermann et al showed the difference between stacking fault‐induced deformation band formation and the high‐pressure modification of ϵ‐iron at 6–8 GPa for the TRIP steel under investigation, which was characterized by a different c/a ratio . Theoretically, the formation of real hexagonal phase boundaries would provoke the generation of characteristic misorientations across the interface during plastic deformation.…”

Section: Resultsmentioning

confidence: 99%

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Deformation Bands in High‐Alloy Austenitic 16Cr6Mn6Ni TRIP Steel: Phase Transformation and Its Consequences on Strain Hardening at Room Temperature

Martin

Wolf

Decker

et al. 2015

steel research int.

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In this study, the formation of deformation bands during plastic deformation in austenite is analysed. The movement of (partial) dislocations on neighboring lattice planes formed pronounced deformation bands, which were identified as e-martensite if the stacking faults are predominantly aligned on every second {111} lattice plane. In these deformation bands, a 0 -martensite nuclei are formed, severely fragmenting the mean free path of dislocations. The strain hardening is found to depend directly on the nucleation rate of a 0 -martensite. The a 0 -martensite nuclei represented effective barriers for (partial) dislocation movement in the deformation bands. On the basis of three different grain sizes, the strain-hardening capability of the martensitic g ! e ! a 0 phase transformation is analysed. Although the triggering stress for nucleation of a 0 -martensite is influenced by grain size, the absolute value of the strain hardening due to a 0 -martensite formation is the same. This is related to the fact that the continuous fragmentation of the dislocation mean free path is in the same order of magnitude for all grain sizes. Using a basic approach that treated the continuous reduction of the dislocation mean free path as a Hall-Petch-like effect, comparable with strain hardening in TWIP steels, the contribution of the effect to the increasing strength in austenitic TRIP steels is estimated.[ Ã ] Dr.

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Section: Resultsmentioning

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Deformation Bands in High‐Alloy Austenitic 16Cr6Mn6Ni TRIP Steel: Phase Transformation and Its Consequences on Strain Hardening at Room Temperature

Martin

Wolf

Decker

et al. 2015

steel research int.

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“…However, other authors have reported in C-containing TWIP steels possible twin formation by the formation of Frank partials [9]. The structure of -martensite is different from the HCP phase in Fe forming at high pressures [10]; in the former, the structure consists of closely spaced stacking faults (deformation bands) within the matrix, whereas in the latter less microstructural defects have been observed, exhibiting a nearly uniform hexagonal structure. α -martensite forms at the intersections of deformation bands (martensite or twins) and its growth is confined to the extent of the bands [11].…”

Section: Introductionmentioning

confidence: 91%

Understanding martensite and twin formation in austenitic steels: A model describing TRIP and TWIP effects

Galindo-Nava

Rivera-Dı́az-del-Castillo

2017

Acta Materialia

221

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A unified description for the evolution of-and α-martensite, and twinning in austenitic steels is presented. The formation of micron-scale and twin bands is obtained by considering the evolution of hierarchically arranged nano-sized and twins (embryos). The critical size and applied stress when these structures form is obtained by minimising their free energy of formation. The difference between forming an plate or a twin lies in the number of overlapping stacking faults in their structure. A nucleation rate criterion is proposed in terms of the critical embryo size, resolved shear stress and embryo number density. Based on Olson and Cohen's classical α-martensite transformation model, the nucleation rate of α is considered proportional to that for. These results, combined with dislocation-based approximations, are employed to prescribe the microstructure and flow stress response in steels where transformation-induced-plasticity (TRIP) and/or twinning-inducedplasticity (TWIP) effects operate; these include austenitic stainless and high-Mn steels. Maps showing the operation range of , α and twinning in terms of the stacking fault energy at different strain levels are defined. Effects of chemical composition in the microstructure and mechanical response in stainless steels are also explored. These results allow identifying potential compositional scenarios when the TRIP and/or TWIP effects are promoted in austenitic steels.

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“…To better clarify this, as is well-known, the α'-martensite may nucleate at the intersections of deformation bands that can be composed by ɛ-martensite and twins in metastable austenitic steels [34,36]. The growth of α'martensite may occur by the nucleation and coalescence of new α'-martensite nuclei repeatedly [35]. Despite the general idea that α'-martensite may form just in low SFE steels [9], however van Tol et al [37] reported small fractions of α'-martensite (<1.2%) in a TWIP steel during deep drawing by SFE of 50 mJ/m 2 .…”

Section: Deformation Mechanismsmentioning

confidence: 96%

The valuation of microstructural evolution in a thermo-mechanically processed transformation-twinning induced plasticity steel during strain hardening

Sabzi

Zarei-Hanzaki

Kaijalainen

et al. 2019

Materials Science and Engineering: A

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The successive evolution of martensitic transformation, twining and dislocation substructure formation in a transformation-twinning induced plasticity steel during room temperature straining was studied in the present work. This was materialized through microstructural observations and micro-texture examinations utilizing the electron backscattered diffraction method. To evaluate the strain hardening behaviour of the thermomechanically processed steel, tensile testing procedure to different strains at ambient temperature was practiced. The results indicated that the dislocation slip, mechanical twinning, and deformation induced ɛ/α'-martensite formation were involved as the deformation mechanisms. At the early stages of deformation, the dynamic formation of dislocation substructure, strain induced ɛ-martensite and twins from austenite played the main role in the observed work hardening behavior. Furthermore, the results demonstrated that the formation of α'-martensite was the dominant deformation mechanism at higher deformation levels. The corresponding texture analysis indicated to a double fibre texture formation, with a relatively stronger <111> at lower strains and a stronger <100> partial fibre parallel to tensile axis at higher strains. However, in the latter, the Cube, A and Goss Twin (GT)type textures were dominated. Decreasing of the Goss and S components were attributed to the preferential transformation of austenite to α'and ɛ-martensites, respectively. The presence of GT component even at higher strains approved the participation of deformation induced twinning as a dominant deformation mechanism up to failure.

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Investigation of Phase Transformations in High-Alloy Austenitic TRIP Steel Under High Pressure (up to 18 GPa) by In Situ Synchrotron X-ray Diffraction and Scanning Electron Microscopy

Cited by 29 publications

References 84 publications

Deformation Bands in High‐Alloy Austenitic 16Cr6Mn6Ni TRIP Steel: Phase Transformation and Its Consequences on Strain Hardening at Room Temperature

Deformation Bands in High‐Alloy Austenitic 16Cr6Mn6Ni TRIP Steel: Phase Transformation and Its Consequences on Strain Hardening at Room Temperature

Understanding martensite and twin formation in austenitic steels: A model describing TRIP and TWIP effects

The valuation of microstructural evolution in a thermo-mechanically processed transformation-twinning induced plasticity steel during strain hardening

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