Retained austenite stability investigation in TRIP steel using neutron diffraction

Zrník, Jozef; Muránsky, Ondrej; Lukáš, P.; Nový, Zbyšek; Šittner, Petr; Horňák, Peter

doi:10.1016/j.msea.2006.04.067

Cited by 25 publications

(12 citation statements)

References 6 publications

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“…Figure 2a further indicates that the effective hardening increases with the initial austenitic volume fraction of the sample, since a sample with a larger initial austenitic volume fraction eventually has more martensite in the microstructure. The phenomenon described above has also been observed experimentally by Zrník et al [3,30] and Jacques et al, [31] where the effect of the initial austenitic volume fraction on the effective stress-strain response of TRIP steels was measured by neutron diffraction analysis. As can be observed in Figure 2b, samples with a larger initial austenitic volume fraction, in general, correspond to a higher rate of transformation (as indicated by the slope of the curves).…”

Section: Effect Of Initial Austenitic Volume Fraction (Phase Morphology)supporting

confidence: 75%

“…[32,33] Despite this restriction, the predictions of the model show a relatively good agreement with experimentally observed trends related to the role of various microstructural parameters in TRIP-assisted steels. [3,[5][6][7]9,30,31] More significantly, the present analysis allows to directly attribute overall mechanical characteristics to the corresponding microstructural parameters, which is a difficult task to perform experimentally.…”

Section: Effect Of Austenitic Grain Sizementioning

confidence: 99%

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A Micromechanical Study of the Deformation Behavior of TRIP‐Assisted Multiphase Steels as a Function of the Microstructural Parameters of the Retained Austenite

et al. 2009

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Steels assisted by transformation-induced plasticity (TRIP steels) are a class of multiphase carbon steels that have interesting mechanical characteristics due to the presence of metastable grains of austenite in their microstructure at room temperature (retained austenite). Upon application of thermal and/or mechanical loading, the grains of retained austenite may transform into martensite, which strongly influences the overall mechanical performance of the steels. Consequently, the stability of retained austenite against transformation is considered to be an important factor in the mechanical performance of this class of steels. Experimental investigations show that the stability of retained austenite is influenced by various microstructural parameters, such as the initial phase volume fractions (phase morphology), [1][2][3] the austenite carbon concentration [1,[4][5][6][7] and the austenitic grain size. [8][9][10] However, in most cases it is difficult to directly measure the individual contributions of these parameters to the stability of retained austenite since, during the processing of experimental samples, microstructural parameters typically cannot be varied independently.In the present work, the overall mechanical behavior of a discrete aggregate of ferritic and austenitic grains, representative of a microstructure of TRIP-assisted steels, is simulated numerically. The goal is to elucidate by means of a parametric study the specific effect of each microstructural parameter on the effective mechanical response, i.e., the effective stressstrain response and the evolution of martensitic transformation. Previous work by the authors was concerned with analyzing the influence of the initial phase volume fractions and carbon concentration [11] and grain size [12] for multiphase TRIP steels with high-yield austenitic phases (which do not deform plastically prior to transformation). In the present analysis, employing the constitutive model presented in Tjahjanto et al., [13] the influence of possible plastic deformations in austenite prior to transformation is taken into account.The results provide important information for further development of the mechanical performance of TRIP steels as well as for the optimization of TRIP steel processing routes. Micromechanical Models, Sample Geometries, and Boundary ConditionsThe type of multiphase steels considered in the present analysis consist of isolated grains of retained austenite embedded in a ferritic matrix. For simplicity, the behavior of the bainitic phase is combined with the effective behavior of the matrix. The constitutive model presented in Tjahjanto et al. [13] is applied to simulate the elastic, plastic, and transformation mechanisms in the austenitic grains and the elasto-plastic response of the ferritic matrix. This model combines the transformation model of Turteltaub and Suiker [14][15][16] [used to simulate the transformation of facecentered cubic (FCC) austenite into body-centered tetragonal (BCT) martensite] with a crystal plasticity model (used...

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Section: Effect Of Initial Austenitic Volume Fraction (Phase Morphology)supporting

confidence: 75%

Section: Effect Of Austenitic Grain Sizementioning

confidence: 99%

A Micromechanical Study of the Deformation Behavior of TRIP‐Assisted Multiphase Steels as a Function of the Microstructural Parameters of the Retained Austenite

et al. 2009

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“…The primary reason for the limited data availability in the literature is that retained austenite, being a metastable phase, cannot be studied in a discrete and independent manner without high-end instrumentation such as synchrotron radiation or neutron diffraction. However, the development of and recent advances in neutron sources have greatly enabled discrete studies at the lattice level that can help in understanding the transformation behavior of individual phases during tensile [9], torsion [10] and cyclic fatigue [11] testing. Neutrons penetrate deeper into the substrate, allowing characterization at the subsurface level that cannot be achieved using any other non-destructive techniques.…”

Section: Introductionmentioning

confidence: 99%

In-situ neutron diffraction and crystal plasticity finite element modeling to study the kinematic stability of retained austenite in bearing steels

Voothaluru

Bedekar

Xie

et al. 2018

Materials Science and Engineering: A

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This work integrates in-situ neutron diffraction and crystal plasticity finite element modeling to study the kinematic stability of retained austenite in high carbon bearing steels. The presence of a kinematically metastable retained austenite in bearing steels can significantly affect the macro-mechanical and micro-mechanical material response. Mechanical characterization of metastable austenite is a critical component in accurately capturing the micro-mechanical behavior under typical application loads. Traditional mechanical characterization techniques are unable to discretely quantify the micro-mechanical response of the austenite , and as a result, the computational predictions rely heavily on trial and error or qualitative descriptions of the austenite phase. In order to overcome this, in the present work, we use in-situ neutron diffraction of a uniaxial tension test of an A485 Grade 1 bearing steel specimen. The mechanical response determined from the neutron diffraction analysis was incorporated into a hybrid crystal plasticity finite element model that accounts for the martensite's crystal plasticity and the stress-assisted transformation from austenite to martensite in bearing steels. The modeling response was used to estimate the single crystal elastic constants of the austenite and martensite phases. The resultsshow that using in-situ neutron diffraction, coupled with a crystal plasticity model, can successfully predict both the micro-mechanical and macro-mechanical responses of bearing steels while accounting for the martensitic transformation of the retained austenite.

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“…martensite and carbides can be present in some cases [2,3]. Improvements in mechanical properties of TRIP-assisted steels are related to relationships between chemical composition and microstructure (grain size, phase morphology and others) and stability of the retained austenite [4]. The stabilization of austenite at room temperature is enhanced by carbon enrichment during heat treatment [5].…”

Section: Trip (Transformation Induced Plasticity) Assisted Steels Belmentioning

confidence: 99%

Effects of Heat Treatment on Morphology, Texture and Mechanical Properties of a MnSiAl Multiphase Steel with TRIP Behavior

Salinas‐Rodríguez¹,

Artigas²,

Ipiña³

et al. 2018

Preprint

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: The effect that the microstructure exerts on the TRIP phenomenon and on the mechanical properties in a multiphase steel was studied. Samples of an initially cold-rolled ferrite-pearlite steel underwent different intercritical annealing treatments at 750 °C until an equal fractions of austenite/ferrite was reached; the intercritical treatment was followed by isothermal bainitic treatments before cooling the samples to room temperature. Samples in the first treatment were heated  directly to the intercritical temperature, whereas other samples were heated to either 900 or 1100 °C to obtain a fully homogenized, single phase austenitic microstructure prior to the conducting the intercritical treatment. The high temperature homogenization of austenite resulted in the decrease in its stability, so a considerable austenite fraction transformed into martensite by cooling to room temperature after the bainitic heat treatment. Most of the retained austenite transformed during the tensile tests, and as a consequence, the previously homogenized steels showed the highest UTS. In turn, the steel with a ferritic-pearlitic initial microstructure, exhibited higher ductility than the other steels and texture components that favor forming processes.     

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Retained austenite stability investigation in TRIP steel using neutron diffraction

Cited by 25 publications

References 6 publications

A Micromechanical Study of the Deformation Behavior of TRIP‐Assisted Multiphase Steels as a Function of the Microstructural Parameters of the Retained Austenite

A Micromechanical Study of the Deformation Behavior of TRIP‐Assisted Multiphase Steels as a Function of the Microstructural Parameters of the Retained Austenite

In-situ neutron diffraction and crystal plasticity finite element modeling to study the kinematic stability of retained austenite in bearing steels

Effects of Heat Treatment on Morphology, Texture and Mechanical Properties of a MnSiAl Multiphase Steel with TRIP Behavior

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