The effects of grain size on yielding, strain hardening, and mechanical twinning in Fe-18Mn-0.6C-1.5Al twinning-induced plasticity steel

Singon Kang, Jae Gil Jung, Mihyun Kang, Wanchuck Woo, Young Kook Lee

Research output: Contribution to journalArticle

38 Citations (Scopus)

Abstract

The objective of the present study was to investigate the influences of grain refinement on yielding, strain hardening, and mechanical twinning during tensile deformation in Fe-high Mn twinning-induced plasticity (TWIP) steel. For this purpose, Fe-18Mn-0.6C-1.5Al TWIP steels with average grain sizes of 2, 10, and 50 μm were tensile tested at room temperature, and their stress-strain and strain hardening rate curves, dislocation densities, and microstructures were measured and analyzed by means of transmission electron microscopy and neutron diffractometry. The stress-strain curves showed a transition from continuous to discontinuous yielding with grain refinement, which was due to a lack of mobile dislocations, not due to mechanical twinning or martensitic transformation. The grain refinement increased the dislocation density, caused the planar to non-planar slip, and retarded primary and secondary mechanical twinning. The strain hardening rate-strain curves of TWIP steels used were able to be divided into five stages by the slope change. Until the stage III, dislocation hardening was predominant; at the stages IV and V mechanical twinning became more contributive to strain hardening. The suppression of both planar dislocation slip and mechanical twinning by grain refinement is most likely due to the increase in the back stress of dislocations on a slip plane, which was caused by the rapid accumulation of dislocations by plastic deformation in the fine-grained TWIP steel. A high level of back stress narrows the width of stacking faults, facilitates the cross slip of dislocations, and reduces the interactions between partial dislocations required for mechanical twinning.

Original languageEnglish
Pages (from-to)212-220
Number of pages9
JournalMaterials Science and Engineering A
Volume652
DOIs
Publication statusPublished - 2016 Jan 15

Fingerprint

mechanical twinning
strain hardening
Steel
Twinning
twinning
Strain hardening
plastic properties
Plasticity
grain size
steels
Dislocations (crystals)
Grain refinement
slip
curves
tensile deformation
martensitic transformation
Martensitic transformations
Stacking faults
crystal defects
hardening

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

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title = "The effects of grain size on yielding, strain hardening, and mechanical twinning in Fe-18Mn-0.6C-1.5Al twinning-induced plasticity steel",
abstract = "The objective of the present study was to investigate the influences of grain refinement on yielding, strain hardening, and mechanical twinning during tensile deformation in Fe-high Mn twinning-induced plasticity (TWIP) steel. For this purpose, Fe-18Mn-0.6C-1.5Al TWIP steels with average grain sizes of 2, 10, and 50 μm were tensile tested at room temperature, and their stress-strain and strain hardening rate curves, dislocation densities, and microstructures were measured and analyzed by means of transmission electron microscopy and neutron diffractometry. The stress-strain curves showed a transition from continuous to discontinuous yielding with grain refinement, which was due to a lack of mobile dislocations, not due to mechanical twinning or martensitic transformation. The grain refinement increased the dislocation density, caused the planar to non-planar slip, and retarded primary and secondary mechanical twinning. The strain hardening rate-strain curves of TWIP steels used were able to be divided into five stages by the slope change. Until the stage III, dislocation hardening was predominant; at the stages IV and V mechanical twinning became more contributive to strain hardening. The suppression of both planar dislocation slip and mechanical twinning by grain refinement is most likely due to the increase in the back stress of dislocations on a slip plane, which was caused by the rapid accumulation of dislocations by plastic deformation in the fine-grained TWIP steel. A high level of back stress narrows the width of stacking faults, facilitates the cross slip of dislocations, and reduces the interactions between partial dislocations required for mechanical twinning.",
author = "Singon Kang and Jung, {Jae Gil} and Mihyun Kang and Wanchuck Woo and Lee, {Young Kook}",
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The effects of grain size on yielding, strain hardening, and mechanical twinning in Fe-18Mn-0.6C-1.5Al twinning-induced plasticity steel. / Kang, Singon; Jung, Jae Gil; Kang, Mihyun; Woo, Wanchuck; Lee, Young Kook.

In: Materials Science and Engineering A, Vol. 652, 15.01.2016, p. 212-220.

Research output: Contribution to journalArticle

TY - JOUR

T1 - The effects of grain size on yielding, strain hardening, and mechanical twinning in Fe-18Mn-0.6C-1.5Al twinning-induced plasticity steel

AU - Kang, Singon

AU - Jung, Jae Gil

AU - Kang, Mihyun

AU - Woo, Wanchuck

AU - Lee, Young Kook

PY - 2016/1/15

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N2 - The objective of the present study was to investigate the influences of grain refinement on yielding, strain hardening, and mechanical twinning during tensile deformation in Fe-high Mn twinning-induced plasticity (TWIP) steel. For this purpose, Fe-18Mn-0.6C-1.5Al TWIP steels with average grain sizes of 2, 10, and 50 μm were tensile tested at room temperature, and their stress-strain and strain hardening rate curves, dislocation densities, and microstructures were measured and analyzed by means of transmission electron microscopy and neutron diffractometry. The stress-strain curves showed a transition from continuous to discontinuous yielding with grain refinement, which was due to a lack of mobile dislocations, not due to mechanical twinning or martensitic transformation. The grain refinement increased the dislocation density, caused the planar to non-planar slip, and retarded primary and secondary mechanical twinning. The strain hardening rate-strain curves of TWIP steels used were able to be divided into five stages by the slope change. Until the stage III, dislocation hardening was predominant; at the stages IV and V mechanical twinning became more contributive to strain hardening. The suppression of both planar dislocation slip and mechanical twinning by grain refinement is most likely due to the increase in the back stress of dislocations on a slip plane, which was caused by the rapid accumulation of dislocations by plastic deformation in the fine-grained TWIP steel. A high level of back stress narrows the width of stacking faults, facilitates the cross slip of dislocations, and reduces the interactions between partial dislocations required for mechanical twinning.

AB - The objective of the present study was to investigate the influences of grain refinement on yielding, strain hardening, and mechanical twinning during tensile deformation in Fe-high Mn twinning-induced plasticity (TWIP) steel. For this purpose, Fe-18Mn-0.6C-1.5Al TWIP steels with average grain sizes of 2, 10, and 50 μm were tensile tested at room temperature, and their stress-strain and strain hardening rate curves, dislocation densities, and microstructures were measured and analyzed by means of transmission electron microscopy and neutron diffractometry. The stress-strain curves showed a transition from continuous to discontinuous yielding with grain refinement, which was due to a lack of mobile dislocations, not due to mechanical twinning or martensitic transformation. The grain refinement increased the dislocation density, caused the planar to non-planar slip, and retarded primary and secondary mechanical twinning. The strain hardening rate-strain curves of TWIP steels used were able to be divided into five stages by the slope change. Until the stage III, dislocation hardening was predominant; at the stages IV and V mechanical twinning became more contributive to strain hardening. The suppression of both planar dislocation slip and mechanical twinning by grain refinement is most likely due to the increase in the back stress of dislocations on a slip plane, which was caused by the rapid accumulation of dislocations by plastic deformation in the fine-grained TWIP steel. A high level of back stress narrows the width of stacking faults, facilitates the cross slip of dislocations, and reduces the interactions between partial dislocations required for mechanical twinning.

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