Stability and mechanical properties of some metastable austenitic steels

Bhandarkar, D.; Zackay, V.F.; Parker, E.R.

doi:10.1007/bf02644238

Cited by 89 publications

(31 citation statements)

References 14 publications

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“…Since the first observations of the TRIP effect in metastable austenitic steels [14,15], a large volume of modelling [5-6, 10, 11, 16-18] and experimental work [5,15,16,18,19] has been aimed at understanding the mechanism. During the austenite to martensite transformation, the macroscopic plastic strain, arises from the shape change as determined by the preferential selection of favourable crystallographic variants (Magee effect [9]) and from the plastic accommodation processes which occur around the forming martensite grains (the Greenwood-Johnson effect) [6,12,16,19]. During deformation-induced transformation, two main factors control the plastic flow behaviour of the material: (i) the dynamic softening arising from plastic straining due to the dilation effect upon formation of martensitic grains [11,17] and, (ii) the static hardening caused by the increasing volume fraction of the harder martensitic phase.…”

Section: Transformation-induced Plasticity Effectmentioning

confidence: 99%

“…As the TRIP phenomenon requires austenite to undergo a phase transition, the term 'austenite stability' is used to describe the resistance of the metastable austenite to form martensite. To this end, a large variety of factors such as the steel composition, the processing history, the stress state and the test environment have been shown to affect austenite stability [15,[19][20][21][22][23].…”

Section: Transformation-induced Plasticity Effectmentioning

confidence: 99%

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Retained Austenite: Transformation-Induced Plasticity

Pereloma¹,

Gazder²,

Timokhina³

2016

Encyclopedia of Iron, Steel, and Their Alloys

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The deformation-induced phase transformation of metastable austenite to martensite is accompanied by macroscopic plastic strain and results in significant work hardening and the delayed onset of necking. Steels that exhibit such transformation-induced plasticity (TRIP) effect possess high strength-ductility ratios and improved toughness. Since the stability of the retained austenite (RA) phase is the rate controlling mechanism for the TRIP effect, the factors affecting the chemical and mechanical stability of RA in CMnSi TRIP steels are discussed. It was suggested that chemical stability plays a more important role at low strains, whereas other factors become responsible for RA behavior at higher strains. The importance of optimizing the processing parameters to achieve the desirable level of austenite stability is highlighted. Finally, the influence of mechanical testing conditions and the interaction between the phases during tensile testing are also detailed. ABSTRACTThe deformation-induced phase transformation of metastable austenite to martensite is accompanied by macroscopic plastic strain and results in significant work hardening and the delayed onset of necking. Steels that exhibit such transformation-induced plasticity (TRIP) effect possess high strength-ductility ratios and improved toughness. Since the stability of the retained austenite phase is the rate controlling mechanism for the TRIP effect, the factors affecting the chemical and mechanical stability of retained austenite in CMnSi TRIP steels are discussed. It was suggested that chemical stability plays a more important role at low strains, whereas other factors become responsible for the RA behavior at higher strains. The importance of optimising the processing parameters to achieve the desirable level of austenite stability was highlighted. Finally, the influence of mechanical testing conditions and the interaction between the phases during tensile testing are also detailed.Eds. R. Colás and G. E. Totten, chapter TRIP effect and retained austenite stability in steels 2

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Section: Transformation-induced Plasticity Effectmentioning

confidence: 99%

Section: Transformation-induced Plasticity Effectmentioning

confidence: 99%

Retained Austenite: Transformation-Induced Plasticity

Pereloma¹,

Gazder²,

Timokhina³

2016

Encyclopedia of Iron, Steel, and Their Alloys

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“…As the phase transformation is accompanied by an increase of the specific volume (DV % 2.3 pct [22] ), a directional elongation of the tensile sample in the direction of loading is achieved spontaneously, resulting in a drop in the measured stress. [42] The increase of YS at temperatures below 213 K (À60°C) could be explained by the athermal a¢-martensite formation (~10 vol pct) during cooling of the sample down to the testing temperature. Consequently, a higher amount of interfacial area is created in the large austenitic grains, and the external load is distributed to the volume fractions of austenite and a¢-martensite.…”

Section: B Correlation With the Mechanical Propertiesmentioning

confidence: 99%

Deformation Mechanisms in Austenitic TRIP/TWIP Steel as a Function of Temperature

Martin

Wolf

Martin

et al. 2014

Metall Mater Trans A

235

106

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A high-alloy austenitic CrMnNi steel was deformed at temperatures between 213 K and 473 K (À60°C and 200°C) and the resulting microstructures were investigated. At low temperatures, the deformation was mainly accompanied by the direct martensitic transformation of c-austenite to a¢-martensite (fcc fi bcc), whereas at ambient temperatures, the transformation via emartensite (fcc fi hcp fi bcc) was observed in deformation bands. Deformation twinning of the austenite became the dominant deformation mechanism at 373 K (100°C), whereas the conventional dislocation glide represented the prevailing deformation mode at 473 K (200°C). The change of the deformation mechanisms was attributed to the temperature dependence of both the driving force of the martensitic c fi a¢ transformation and the stacking fault energy of the austenite. The continuous transition between the e-martensite formation and the twinning could be explained by different stacking fault arrangements on every second and on each successive {111} austenite lattice plane, respectively, when the stacking fault energy increased. A continuous transition between the transformation-induced plasticity effect and the twinninginduced plasticity effect was observed with increasing deformation temperature. Whereas the formation of a¢-martensite was mainly responsible for increased work hardening, the stacking fault configurations forming e-martensite and twins induced additional elongation during tensile testing.

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“…The strain can arise from transformation shape change or plastic accommodation process, which occur around the martensite islands as they form. [8] The fatigue performance of a vehicle is an important design and material selection consideration due to the repeated loads/strains that are experienced during normal use. While the vehicle is designed so that the stresses in a component are below the yield stress of the material, there are regions of stress concentration in the body structure that can generate small plastic strains.…”

Section: Introductionmentioning

confidence: 99%

Cyclic Deformation of Advanced High-Strength Steels: Mechanical Behavior and Microstructural Analysis

Hilditch

Timokhina

Robertson

et al. 2009

Metall Mater Trans A

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The fatigue properties of multiphase steels are an important consideration in the automotive industry. The different microstructural phases present in these steels can influence the strain life and cyclic stabilized strength of the material due to the way in which these phases accommodate the applied cyclic strain. Fully reversed strain-controlled low-cycle fatigue tests have been used to determine the mechanical fatigue performance of a dual-phase (DP) 590 and transformationinduced plasticity (TRIP) 780 steel, with transmission electron microscopy (TEM) used to examine the deformed microstructures. It is shown that the higher strain life and cyclic stabilized strength of the TRIP steel can be attributed to an increased yield strength. Despite the presence of significant levels of retained austenite in the TRIP steel, both steels exhibited similar cyclic softening behavior at a range of strain amplitudes due to comparable ferrite volume fractions and yielding characteristics. Both steels formed low-energy dislocation structures in the ferrite during cyclic straining.

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Stability and mechanical properties of some metastable austenitic steels

Cited by 89 publications

References 14 publications

Retained Austenite: Transformation-Induced Plasticity

Retained Austenite: Transformation-Induced Plasticity

Deformation Mechanisms in Austenitic TRIP/TWIP Steel as a Function of Temperature

Cyclic Deformation of Advanced High-Strength Steels: Mechanical Behavior and Microstructural Analysis

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