Novel medium-Mn (austenite + martensite) duplex hot-rolled steel achieving 1.6 GPa strength with 20 % ductility by Mn-segregation-induced TRIP mechanism

Hyungsoo Lee, Min Chul Jo, Seok S Sohn, A. Zargaran, Joo Hyun Ryu, Nack J. Kim, Sunghak Lee

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Ultra-high-strength (over 1 GPa) hot-rolled steel sheets have been actively developed to protect passengers in cases of vehicle crashes, and their applications have been expanded to cold-rolled steel sheets. A major alloying element for forming meta-stable austenite is Mn in (austenite + martensite) duplex microstructures, which is readily obtained at medium-Mn level ((3–10) wt.%). However, these medium-Mn hot-rolled duplex microstructures inevitably include Mn-segregated bands, which often lead to anisotropic mechanical properties and deteriorate the strength or uniform elongation. However, in this study, we show favorable effects of the Mn-segregated band, by carefully controlling the composition, size, and shape of austenite in Mn-rich and Mn-lean bands in medium-Mn duplex steels (composition; Fe-0.1C-10Mn-1Si-0.3Mo-0.5 V (wt.%)). The austenite grown coarsely in the Mn-rich band provoked transformation-induced plasticity (TRIP) more efficiently than the austenite finely transformed from the martensite in the Mn-lean band. The Mn composition acted more dominantly on the austenite stability than the austenite size, resulting in continuous TRIP in the austenite of the Mn-rich band. This austenite enables continuous strain hardening, thereby leading to high yield and tensile strengths of (1.0–1.6) GPa together with large ductility of 20%, which offers promise for new applications to ultra-high-strength automotive hot-rolled steel sheets.

Original languageEnglish
Pages (from-to)247-260
Number of pages14
JournalActa Materialia
Volume147
DOIs
Publication statusPublished - 2018 Apr 1
Externally publishedYes

Fingerprint

Steel
Martensite
Austenite
Plasticity
Ductility
Steel sheet
Chemical analysis
Microstructure
Alloying elements
Strain hardening
Yield stress
Elongation
Tensile strength
Mechanical properties

Keywords

  • Austenite stability
  • Duplex steel
  • Hot-rolled steel
  • Mn segregation
  • TRansformation Induced Plasticity (TRIP)

ASJC Scopus subject areas

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

Cite this

Novel medium-Mn (austenite + martensite) duplex hot-rolled steel achieving 1.6 GPa strength with 20 % ductility by Mn-segregation-induced TRIP mechanism. / Lee, Hyungsoo; Jo, Min Chul; Sohn, Seok S; Zargaran, A.; Ryu, Joo Hyun; Kim, Nack J.; Lee, Sunghak.

In: Acta Materialia, Vol. 147, 01.04.2018, p. 247-260.

Research output: Contribution to journalArticle

Lee, Hyungsoo ; Jo, Min Chul ; Sohn, Seok S ; Zargaran, A. ; Ryu, Joo Hyun ; Kim, Nack J. ; Lee, Sunghak. / Novel medium-Mn (austenite + martensite) duplex hot-rolled steel achieving 1.6 GPa strength with 20 % ductility by Mn-segregation-induced TRIP mechanism. In: Acta Materialia. 2018 ; Vol. 147. pp. 247-260.
@article{aa0545bcfff7497fb74509dcf234d64e,
title = "Novel medium-Mn (austenite + martensite) duplex hot-rolled steel achieving 1.6 GPa strength with 20 {\%} ductility by Mn-segregation-induced TRIP mechanism",
abstract = "Ultra-high-strength (over 1 GPa) hot-rolled steel sheets have been actively developed to protect passengers in cases of vehicle crashes, and their applications have been expanded to cold-rolled steel sheets. A major alloying element for forming meta-stable austenite is Mn in (austenite + martensite) duplex microstructures, which is readily obtained at medium-Mn level ((3–10) wt.{\%}). However, these medium-Mn hot-rolled duplex microstructures inevitably include Mn-segregated bands, which often lead to anisotropic mechanical properties and deteriorate the strength or uniform elongation. However, in this study, we show favorable effects of the Mn-segregated band, by carefully controlling the composition, size, and shape of austenite in Mn-rich and Mn-lean bands in medium-Mn duplex steels (composition; Fe-0.1C-10Mn-1Si-0.3Mo-0.5 V (wt.{\%})). The austenite grown coarsely in the Mn-rich band provoked transformation-induced plasticity (TRIP) more efficiently than the austenite finely transformed from the martensite in the Mn-lean band. The Mn composition acted more dominantly on the austenite stability than the austenite size, resulting in continuous TRIP in the austenite of the Mn-rich band. This austenite enables continuous strain hardening, thereby leading to high yield and tensile strengths of (1.0–1.6) GPa together with large ductility of 20{\%}, which offers promise for new applications to ultra-high-strength automotive hot-rolled steel sheets.",
keywords = "Austenite stability, Duplex steel, Hot-rolled steel, Mn segregation, TRansformation Induced Plasticity (TRIP)",
author = "Hyungsoo Lee and Jo, {Min Chul} and Sohn, {Seok S} and A. Zargaran and Ryu, {Joo Hyun} and Kim, {Nack J.} and Sunghak Lee",
year = "2018",
month = "4",
day = "1",
doi = "10.1016/j.actamat.2018.01.033",
language = "English",
volume = "147",
pages = "247--260",
journal = "Acta Materialia",
issn = "1359-6454",
publisher = "Elsevier Limited",

}

TY - JOUR

T1 - Novel medium-Mn (austenite + martensite) duplex hot-rolled steel achieving 1.6 GPa strength with 20 % ductility by Mn-segregation-induced TRIP mechanism

AU - Lee, Hyungsoo

AU - Jo, Min Chul

AU - Sohn, Seok S

AU - Zargaran, A.

AU - Ryu, Joo Hyun

AU - Kim, Nack J.

AU - Lee, Sunghak

PY - 2018/4/1

Y1 - 2018/4/1

N2 - Ultra-high-strength (over 1 GPa) hot-rolled steel sheets have been actively developed to protect passengers in cases of vehicle crashes, and their applications have been expanded to cold-rolled steel sheets. A major alloying element for forming meta-stable austenite is Mn in (austenite + martensite) duplex microstructures, which is readily obtained at medium-Mn level ((3–10) wt.%). However, these medium-Mn hot-rolled duplex microstructures inevitably include Mn-segregated bands, which often lead to anisotropic mechanical properties and deteriorate the strength or uniform elongation. However, in this study, we show favorable effects of the Mn-segregated band, by carefully controlling the composition, size, and shape of austenite in Mn-rich and Mn-lean bands in medium-Mn duplex steels (composition; Fe-0.1C-10Mn-1Si-0.3Mo-0.5 V (wt.%)). The austenite grown coarsely in the Mn-rich band provoked transformation-induced plasticity (TRIP) more efficiently than the austenite finely transformed from the martensite in the Mn-lean band. The Mn composition acted more dominantly on the austenite stability than the austenite size, resulting in continuous TRIP in the austenite of the Mn-rich band. This austenite enables continuous strain hardening, thereby leading to high yield and tensile strengths of (1.0–1.6) GPa together with large ductility of 20%, which offers promise for new applications to ultra-high-strength automotive hot-rolled steel sheets.

AB - Ultra-high-strength (over 1 GPa) hot-rolled steel sheets have been actively developed to protect passengers in cases of vehicle crashes, and their applications have been expanded to cold-rolled steel sheets. A major alloying element for forming meta-stable austenite is Mn in (austenite + martensite) duplex microstructures, which is readily obtained at medium-Mn level ((3–10) wt.%). However, these medium-Mn hot-rolled duplex microstructures inevitably include Mn-segregated bands, which often lead to anisotropic mechanical properties and deteriorate the strength or uniform elongation. However, in this study, we show favorable effects of the Mn-segregated band, by carefully controlling the composition, size, and shape of austenite in Mn-rich and Mn-lean bands in medium-Mn duplex steels (composition; Fe-0.1C-10Mn-1Si-0.3Mo-0.5 V (wt.%)). The austenite grown coarsely in the Mn-rich band provoked transformation-induced plasticity (TRIP) more efficiently than the austenite finely transformed from the martensite in the Mn-lean band. The Mn composition acted more dominantly on the austenite stability than the austenite size, resulting in continuous TRIP in the austenite of the Mn-rich band. This austenite enables continuous strain hardening, thereby leading to high yield and tensile strengths of (1.0–1.6) GPa together with large ductility of 20%, which offers promise for new applications to ultra-high-strength automotive hot-rolled steel sheets.

KW - Austenite stability

KW - Duplex steel

KW - Hot-rolled steel

KW - Mn segregation

KW - TRansformation Induced Plasticity (TRIP)

UR - http://www.scopus.com/inward/record.url?scp=85041411196&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85041411196&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2018.01.033

DO - 10.1016/j.actamat.2018.01.033

M3 - Article

AN - SCOPUS:85041411196

VL - 147

SP - 247

EP - 260

JO - Acta Materialia

JF - Acta Materialia

SN - 1359-6454

ER -