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Title: Characterization of twin boundaries in an Fe–17.5Mn–0.56C twinning induced plasticity steel

Abstract

A twinning-induced plasticity steel of composition Fe–17.5 wt.% Mn–0.56 wt.% C–1.39 wt.% Al–0.24 wt.% Si was analyzed for the purpose of characterizing the relationship between tensile strain and deformation twinning. Tensile samples achieved a maximum of 0.46 true strain at failure, and a maximum ultimate tensile strength of 1599 MPa. Electron backscatter diffraction (EBSD) analysis showed that the grain orientation rotated heavily to < 111 > parallel to the tensile axis above 0.3 true strain. Sigma 3 misorientations, as identified by EBSD orientation measurements, and using the image quality maps were used to quantify the number of twins present in the scanned areas of the samples. The image quality method yielded a distinct positive correlation between the twin area density and deformation, but the orientation measurements were unreliable in quantifying twin density in these structures. Quantitative analysis of the twin fraction is limited from orientation information because of the poor spatial resolution of EBSD in relation to the twin thickness. The EBSD orientation maps created for a thin foil sample showed some improvement in the resolution of the twins, but not enough to be significant. Measurements of the twins in the transmission electron microscopy micrographs yielded an average thickness ofmore » 23 nm, which is near the resolution capabilities of EBSD on this material for the instrumentation used. Electron channeling contrast imaging performed on one bulk tensile specimen of 0.34 true strain, using a method of controlled diffraction, yielded several images of twinning, dislocation structures and strain fields. A twin thickness of 66 nm was measured by the same method used for the transmission electron microscopy measurement. It is apparent that the results obtain by electron channeling contrast imaging were better than those by EBSD but did not capture all information on the twin boundaries such as was observed by transmission electron microscopy. - Highlights: • Performed tensile tests to assess mechanical performance of TWIP alloy • Analyzed tensile specimens using EBSD, TEM, and ECCI • EBSD showed that most twinning occurred at or near the < 111 >//TA orientation. • EBSD, TEM and ECCI were used to measure average twin density. • Compared spatial resolution of EBSD, ECCI and TEM for the instrumentation used.« less

Authors:
 [1];  [1];  [2];  [3]
  1. School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164-2920 (United States)
  2. LEM3, CNRS UMP 7239, Université de Lorraine, 57045 Metz (France)
  3. (DAMAS), Université de Lorraine, 57045 Metz (France)
Publication Date:
OSTI Identifier:
22288681
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 85; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; BACKSCATTERING; DEFORMATION; DENSITY; DISLOCATIONS; ELECTRON CHANNELING; ELECTRON DIFFRACTION; GRAIN ORIENTATION; PLASTICITY; SPATIAL RESOLUTION; STEELS; TENSILE PROPERTIES; TRANSMISSION ELECTRON MICROSCOPY

Citation Formats

Patterson, Erin E., E-mail: erin.diedrich@yahoo.com, Field, David P., E-mail: dfield@wsu.edu, Zhang, Yudong, E-mail: yudong.zhang@univ-metz.fr, and Laboratory of Excellence on Design of Alloy Metals for low mAss Structures. Characterization of twin boundaries in an Fe–17.5Mn–0.56C twinning induced plasticity steel. United States: N. p., 2013. Web. doi:10.1016/J.MATCHAR.2013.08.016.
Patterson, Erin E., E-mail: erin.diedrich@yahoo.com, Field, David P., E-mail: dfield@wsu.edu, Zhang, Yudong, E-mail: yudong.zhang@univ-metz.fr, & Laboratory of Excellence on Design of Alloy Metals for low mAss Structures. Characterization of twin boundaries in an Fe–17.5Mn–0.56C twinning induced plasticity steel. United States. doi:10.1016/J.MATCHAR.2013.08.016.
Patterson, Erin E., E-mail: erin.diedrich@yahoo.com, Field, David P., E-mail: dfield@wsu.edu, Zhang, Yudong, E-mail: yudong.zhang@univ-metz.fr, and Laboratory of Excellence on Design of Alloy Metals for low mAss Structures. Fri . "Characterization of twin boundaries in an Fe–17.5Mn–0.56C twinning induced plasticity steel". United States. doi:10.1016/J.MATCHAR.2013.08.016.
@article{osti_22288681,
title = {Characterization of twin boundaries in an Fe–17.5Mn–0.56C twinning induced plasticity steel},
author = {Patterson, Erin E., E-mail: erin.diedrich@yahoo.com and Field, David P., E-mail: dfield@wsu.edu and Zhang, Yudong, E-mail: yudong.zhang@univ-metz.fr and Laboratory of Excellence on Design of Alloy Metals for low mAss Structures},
abstractNote = {A twinning-induced plasticity steel of composition Fe–17.5 wt.% Mn–0.56 wt.% C–1.39 wt.% Al–0.24 wt.% Si was analyzed for the purpose of characterizing the relationship between tensile strain and deformation twinning. Tensile samples achieved a maximum of 0.46 true strain at failure, and a maximum ultimate tensile strength of 1599 MPa. Electron backscatter diffraction (EBSD) analysis showed that the grain orientation rotated heavily to < 111 > parallel to the tensile axis above 0.3 true strain. Sigma 3 misorientations, as identified by EBSD orientation measurements, and using the image quality maps were used to quantify the number of twins present in the scanned areas of the samples. The image quality method yielded a distinct positive correlation between the twin area density and deformation, but the orientation measurements were unreliable in quantifying twin density in these structures. Quantitative analysis of the twin fraction is limited from orientation information because of the poor spatial resolution of EBSD in relation to the twin thickness. The EBSD orientation maps created for a thin foil sample showed some improvement in the resolution of the twins, but not enough to be significant. Measurements of the twins in the transmission electron microscopy micrographs yielded an average thickness of 23 nm, which is near the resolution capabilities of EBSD on this material for the instrumentation used. Electron channeling contrast imaging performed on one bulk tensile specimen of 0.34 true strain, using a method of controlled diffraction, yielded several images of twinning, dislocation structures and strain fields. A twin thickness of 66 nm was measured by the same method used for the transmission electron microscopy measurement. It is apparent that the results obtain by electron channeling contrast imaging were better than those by EBSD but did not capture all information on the twin boundaries such as was observed by transmission electron microscopy. - Highlights: • Performed tensile tests to assess mechanical performance of TWIP alloy • Analyzed tensile specimens using EBSD, TEM, and ECCI • EBSD showed that most twinning occurred at or near the < 111 >//TA orientation. • EBSD, TEM and ECCI were used to measure average twin density. • Compared spatial resolution of EBSD, ECCI and TEM for the instrumentation used.},
doi = {10.1016/J.MATCHAR.2013.08.016},
journal = {Materials Characterization},
number = ,
volume = 85,
place = {United States},
year = {Fri Nov 15 00:00:00 EST 2013},
month = {Fri Nov 15 00:00:00 EST 2013}
}
  • The surface oxides of twinning-induced plasticity (TWIP) steel annealed at 800 °C for 43 s were investigated using transmission electron microscopy. During the annealing process, the oxygen potential was controlled by adjusting the dew point in a 15%H{sub 2}–N{sub 2} gas atmosphere. It was found that the type of surface oxides formed and the thickness of the oxide layer were determined by the dew point. In a gas mixture with a dew point of − 20 °C, a MnO layer with a thickness of ∼ 100 nm was formed uniformly on the steel surface. Under the MnO layer, a MnAl{submore » 2}O{sub 4} layer with a thickness of ∼ 15 nm was formed with small Mn{sub 2}SiO{sub 4} particles that measured ∼ 70 nm in diameter. Approximately 500 nm below the MnAl{sub 2}O{sub 4} layer, Al{sub 2}O{sub 3} was formed at the grain boundaries. On the other hand, in a gas mixture with a dew point of − 40 °C, a MnAl{sub 2}O{sub 4} layer with a thickness of ∼ 5 nm was formed on most parts of the surface. On some parts of the surface, Mn{sub 2}SiO{sub 4} particles were formed irregularly up to a thickness of ∼ 50 nm. Approximately 200 nm below the MnAl{sub 2}O{sub 4} layer, Al{sub 2}O{sub 3} was found at the grain boundaries. Thermodynamic calculations were performed to explain the experimental results. The calculations showed that when a{sub O2} > ∼ 1.26 × 10{sup −28}, MnO, MnAl{sub 2}O{sub 4}, and Mn{sub 2}SiO{sub 4} can be formed together, and the major oxide is MnO. When a{sub O2} is in the range of 1.26 × 10{sup −28}–2.51 × 10{sup −31}, MnO is not stable but MnAl{sub 2}O{sub 4} is the major oxide. When a{sub O2} < ∼ 2.51 × 10{sup −31}, only Al{sub 2}O{sub 3} is stable. Consequently, the effective activity of oxygen is considered the dominant factor in determining the type and shape of surface oxides of TWIP steel. - Highlights: • The surface oxides of TWIP steel annealed at 800 °C were investigated using TEM. • The surface oxides were determined by the dew point during the annealing process. • The activity of oxygen is the major factor determining the oxides of TWIP steel.« less
  • In-situ neutron diffraction during cyclic tension-compression loading (∼+3.5% to −2.8%) of a 17Mn-3Al-2Si-1Ni-0.06C steel that exhibits concurrent transformation and twinning -induced plasticity effects indicated a significant contribution of intragranular back stresses to the observed Bauschinger effect. Rietveld analysis revealed a higher rate of martensitic transformation during tension compared to compression. Throughout cycling, α′-martensite exhibited the highest phase strains such that it bears an increasing portion of the macroscopic load as its weight fraction evolves. On the other hand, the ε-martensite strain remained compressive as it accommodated most of the internal strains caused by the shape misfit associated with the γ→εmore » and/or ε→α′ transformations.« less
  • Grain orientation dependent behavior during tension-compression type of fatigue loading in a TWIP steel was studied using in-situ neutron diffraction. Orientation zones with dominant behavior of (1) twinning-de-twinning, (2) twinning-re-twinning followed by twinning-de-twinning, (3) twinning followed by dislocation slip and (4) dislocation slip were identified. Jumps of the orientation density were evidenced in neutron diffraction peaks which explains the macroscopic asymmetric behavior. The asymmetric behavior in early stage of fatigue loading is mainly due to small volume fraction of twins in comparison with that at later stage. As a result, easy activation of the de-twin makes the macroscopically unloading behaviormore » nonlinear.« less
  • Inelastic deformation is generally known to aid the kinetics process of solid-state phase transformations either by an increased strain energy or generating new catalyzing defect sites for transformation. The deformation induced martensitic transformation can thus be divided into two categories, viz. stress-assisted and strain-induced transformation. In the present study, the transformation kinetics of {epsilon}-martensite as well as the formation kinetics of deformation twin during inelastic deformation has been investigated experimentally by conducting a series of tensile tests using an austenitic Fe-25Mn-0.2C steel at the various temperatures ranging from 7.5 C to 277 C. When this steel was plastically deformed, bothmore » the {epsilon}-martensite and deformation twin were observed at the temperatures ranging from 7.5 to 57 C, while only the deformation twins were observed at the higher temperatures between 127 C and 177 C. The volume fractions of transformed {epsilon}-martensite and deformation twin were measured by using the usual X-ray diffraction method and the point counting method, respectively. The transformation behavior for both the deformation twin and {epsilon}-martensite formation was then analyzed using the recently proposed kinetics relation, in which the deformation induced phase transformation is viewed as an effective relaxation process to relieve the internal strain energy accumulating during inelastic deformation.« less
  • Previous theoretical and experimental studies demonstrate that small bulk concentrations of impurity and solute elements can segregate to grain boundaries in ferritic steels during cooling from high temperatures. This results from solute-vacancy pair formation and their subsequent diffusion to the grain boundary sinks. The grain boundary segregation which results from cooling at three different rates from fixed temperatures of 1,273 and 1,323 K respectively, have been measured on ferritic Fe-3 wt%Ni alloys and 2[1/4]wt%Cr-1wt%Mo steels containing additions of either P or Sn. In addition, a C-Mn submerged arc weld metal subject to a complex thermal cycle has been investigated. Themore » composition of the grain boundaries have been measured on thin foil specimens using both conventional and high resolution STEM-EDS X-ray microanalysis techniques. Segregations of both P and Sn have been observed in the Fe-3 wt%Ni alloys and 2[1/4]wt%Cr-1wt%Mo steels and P segregations in the weld metal. The measured grain boundary segregations of both P and Sn are discussed with respect to previous theoretical predictions for the cooling rates investigated and the interactive role of other elements present.« less