Investigation of Plastic Instability in TWIP Steels by In Situ Diffraction of High Energy X-Rays

Chateau-Cornu, Jean Philippe; Jacques, Alain; Tinnes, Jean Philippe; Schenk, Thomas

doi:10.4028/www.scientific.net/MSF.783-786.1105

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HomeMaterials Science ForumTHERMEC 2013Investigation of Plastic Instability in TWIP...

Investigation of Plastic Instability in TWIP Steels by In Situ Diffraction of High Energy X-Rays

Abstract:

We investigate the non uniform plastic deformation of a TWIP FeMnC steel by diffraction of high energy synchrotron X-rays. In particular, we observe the propagation of bands of plastic strain localisation. Debye-Scherrer rings are recorded in situ during tensile tests at two different strain rates. Discontinuous initial rings characteristic of unstrained polycristals with no texture become rapidly continuous after several percents of plastic strain due to strain gradients within the grains and a strong texture develops. The crystallographic dependence of the Young’s modulus is estimated and is consistent with the elastic anisotropy of a cubic crystal. A delay between the serrations on the macroscopic tensile curve and the stepwise variations of the diffracted peak’s position and width are consistent with propagating bands nucleating outside the X-ray beam. Slower and thinner bands are observed at the lowest strain rate. A tensile test interrupted to perform a few minute relaxation leads to a displacement of the nucleation site of the bands from one end to the middle of the gauge part.

Info:

Periodical:

Materials Science Forum (Volumes 783-786)

Main Theme:

THERMEC 2013

Edited by:

B. Mishra, M. Ionescu and T. Chandra

Pages:

1105-1110

DOI:

https://doi.org/10.4028/www.scientific.net/MSF.783-786.1105

Citation:

J. P. Chateau-Cornu et al., "Investigation of Plastic Instability in TWIP Steels by In Situ Diffraction of High Energy X-Rays", Materials Science Forum, Vols. 783-786, pp. 1105-1110, 2014

Online since:

May 2014

Authors:

Jean Philippe Chateau-Cornu *, Alain Jacques, Jean Philippe Tinnes, Thomas Schenk

Keywords:

Band Propagation, Dynamic Strain Aging (DSA), Elastic Constants, High Energy XRD, In Situ Diffraction, TWIP Steel

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References

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Paper TitlePages

Mechanical Properties and Microstructure of AZ31 Magnesium Alloy under Uni-Axial Tensile Loading

Authors: Xiao Yu Zhong, Guang Jie Huang, Fang Fang He, Qing Liu

Abstract: Uni-axial tensile plastic deformation behavior of rolled magnesium alloy AZ31B under the temperature range from room temperature(RT) to 250°C with strain rates between 10^-3 and 10^-1s^-1 has been systematically investigated. Microstructure evolution and texture were determined using optical microscopy (OM) and electron back-scattered diffraction (EBSD) techniques, respectively. Our results indicated that the strength and elongation-to-fracture were more sensitive to strain rates at elevated temperature rather than that at room temperature; dynamic recrystallization (DRX) and relaxation of stress at elevated temperature resulted in dramatic change of mechanical properties. Compared with strain rate, the temperature played a more important role in ductility of AZ31B Mg alloy sheet.

219

A Constitutive Model for the Simulation of the Deformation Behavior of TWIP Steels

Authors: André Haufe, Andrea Erhart, Alexander Butz

Abstract: Due to their high strength (tensile strength > 1GPa) in combination with an extreme ductility (failure strain 30-50%) TWinning Induced Plasticity–steels (TWIP-steels) can be considered as promising materials for the production of lightweight automotive components. The industrial application of TWIP-steels requires a fundamental experimental validation of the mechanical behavior as basis for an user-friendly but at the same time accurate constitutive framework and its implementation into commercial Finite Element codes. Related investigations and implementations in order to allow for the simulation of TWIP-steel forming processes are currently conducted within the research project “TWIP4EU”, executed as a cooperation of Fraunhofer - Institut für Werkstoffmechanik IWM in Freiburg (Germany), Salzgitter Mannesmann Forschung GmbH (Germany), Swerea KIMAB (Sweden), Faurecia Autositze GmbH (Germany / France), DYNAmore GmbH (Germany) and ESI GmbH Engineering System (Germany / France).The monotonic one-dimensional hardening behavior of TWIP-steels as a function of the twin volume fraction and dislocation density has been described by Bouaziz et al. (2008), Bouaziz et al. (2011). This model has been proven to be adequate for the description of the flow behavior of TWIP-steels and serves as basis for the constitutive model, presented here. This Bouaziz-model has been extended to a three-dimensional elasto-plastic formulation, including the influence of different loading conditions, anisotropy and kinematic hardening. The present paper deals with the implementation for solids and shells in the commercial Finite Element Code LS-DYNA^® and appropriate validation simulations will be presented.

411

Implementation of a Constitutive Model for the Mechanical Behavior of TWIP Steels and Validation Simulations

Authors: Andrea Erhart, André Haufe, Alexander Butz, Maksim Zapara, Dirk Helm

Abstract: High manganese content TWinning Induced Plasticity (TWIP) steels are promising for the production of lightweight components due to their high strength combined with extreme ductility, see [1]. This paper deals with the implementation of a constitutive model for the macroscopic deformation behavior of TWIP steels under mechanical loading with the aim of simulating metal forming processes and representing the behavior of TWIP-steel components – for example under crash loading - with the Finite Element code LS-DYNA^® and refers to our recently published papers: [2],[4],[5]. Within the present paper we focus on the implementation of the model formulated in [2] and its extension to stress dependent twinning effects.

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