Tensile properties and deformation mode of Si-added Fe-18Mn-0.6C steels

Sang Min Lee, Seung Joon Lee, Sukjin Lee, Jae Hoon Nam, Young-Kook Lee

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The effects of Si concentration and austenite grain size (AGS) on the tensile properties, stacking fault energy (γ), and deformation mode of Fe-18Mn-0.6C (wt.%) steel were investigated to improve the yield strength (YS) of twinning-induced plasticity (TWIP) steel. The 3% Si-added steel revealed the higher YS than previous TWIP steels at the same level of AGS. In particular when the AGS was ∼6.8 μm, its YS reached ∼593 MPa, which is comparable to the YS (613 MPa) of transformation-induced plasticity steel with a tensile strength of 980 MPa. The measured γ of 3% Si-added steel was exponentially decreased with grain coarsening primarily due to the reduction of micro-strain, finally reaching its intrinsic γ (γint) at the AGSs above ∼70 μm. This indicates that the γint measurement by means of X-ray diffractometry must be performed using coarse-grained specimens with the AGSs above ∼70 μm. Critical resolved shear stresses for twinning (τtwin) and ε-martensitic transformation (τε-mart) were evaluated as a function of AGS in (0-3%) Si-added steels. Whereas the τtwin value was slightly decreased with increasing AGS or Si concentration, the τε-mart value was more significantly reduced. This indicates that ε-martensitic transformation precedes mechanical twinning with increasing AGS or Si concentration. As a result, a transition of deformation mode from mechanical twinning to ε-martensitic transformation occurred with grain coarsening in Si-added steels. A critical AGS for the transition of deformation mode was reduced from ∼69 μm to ∼15 μm with increasing Si concentration from 0.5 wt.% to 3.0 wt.%.

Original languageEnglish
Pages (from-to)738-747
Number of pages10
JournalActa Materialia
Volume144
DOIs
Publication statusPublished - 2018 Feb 1

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Steel
Tensile properties
Twinning
Austenite
Yield stress
Martensitic transformations
Plasticity
Coarsening
Stacking faults
X ray diffraction analysis
Shear stress
Tensile strength

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

Cite this

Lee, Sang Min ; Lee, Seung Joon ; Lee, Sukjin ; Nam, Jae Hoon ; Lee, Young-Kook. / Tensile properties and deformation mode of Si-added Fe-18Mn-0.6C steels. In: Acta Materialia. 2018 ; Vol. 144. pp. 738-747.
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abstract = "The effects of Si concentration and austenite grain size (AGS) on the tensile properties, stacking fault energy (γ), and deformation mode of Fe-18Mn-0.6C (wt.{\%}) steel were investigated to improve the yield strength (YS) of twinning-induced plasticity (TWIP) steel. The 3{\%} Si-added steel revealed the higher YS than previous TWIP steels at the same level of AGS. In particular when the AGS was ∼6.8 μm, its YS reached ∼593 MPa, which is comparable to the YS (613 MPa) of transformation-induced plasticity steel with a tensile strength of 980 MPa. The measured γ of 3{\%} Si-added steel was exponentially decreased with grain coarsening primarily due to the reduction of micro-strain, finally reaching its intrinsic γ (γint) at the AGSs above ∼70 μm. This indicates that the γint measurement by means of X-ray diffractometry must be performed using coarse-grained specimens with the AGSs above ∼70 μm. Critical resolved shear stresses for twinning (τtwin) and ε-martensitic transformation (τε-mart) were evaluated as a function of AGS in (0-3{\%}) Si-added steels. Whereas the τtwin value was slightly decreased with increasing AGS or Si concentration, the τε-mart value was more significantly reduced. This indicates that ε-martensitic transformation precedes mechanical twinning with increasing AGS or Si concentration. As a result, a transition of deformation mode from mechanical twinning to ε-martensitic transformation occurred with grain coarsening in Si-added steels. A critical AGS for the transition of deformation mode was reduced from ∼69 μm to ∼15 μm with increasing Si concentration from 0.5 wt.{\%} to 3.0 wt.{\%}.",
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Tensile properties and deformation mode of Si-added Fe-18Mn-0.6C steels. / Lee, Sang Min; Lee, Seung Joon; Lee, Sukjin; Nam, Jae Hoon; Lee, Young-Kook.

In: Acta Materialia, Vol. 144, 01.02.2018, p. 738-747.

Research output: Contribution to journalArticle

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AB - The effects of Si concentration and austenite grain size (AGS) on the tensile properties, stacking fault energy (γ), and deformation mode of Fe-18Mn-0.6C (wt.%) steel were investigated to improve the yield strength (YS) of twinning-induced plasticity (TWIP) steel. The 3% Si-added steel revealed the higher YS than previous TWIP steels at the same level of AGS. In particular when the AGS was ∼6.8 μm, its YS reached ∼593 MPa, which is comparable to the YS (613 MPa) of transformation-induced plasticity steel with a tensile strength of 980 MPa. The measured γ of 3% Si-added steel was exponentially decreased with grain coarsening primarily due to the reduction of micro-strain, finally reaching its intrinsic γ (γint) at the AGSs above ∼70 μm. This indicates that the γint measurement by means of X-ray diffractometry must be performed using coarse-grained specimens with the AGSs above ∼70 μm. Critical resolved shear stresses for twinning (τtwin) and ε-martensitic transformation (τε-mart) were evaluated as a function of AGS in (0-3%) Si-added steels. Whereas the τtwin value was slightly decreased with increasing AGS or Si concentration, the τε-mart value was more significantly reduced. This indicates that ε-martensitic transformation precedes mechanical twinning with increasing AGS or Si concentration. As a result, a transition of deformation mode from mechanical twinning to ε-martensitic transformation occurred with grain coarsening in Si-added steels. A critical AGS for the transition of deformation mode was reduced from ∼69 μm to ∼15 μm with increasing Si concentration from 0.5 wt.% to 3.0 wt.%.

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