Exceptional combination of ultra-high strength and excellent ductility by inevitably generated Mn-segregation in austenitic steel

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

doi:10.1016/j.msea.2018.09.024

Exceptional combination of ultra-high strength and excellent ductility by inevitably generated Mn-segregation in austenitic steel

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

Research output: Contribution to journal › Article › peer-review

9 Citations (Scopus)

Abstract

Austenitic high-Mn steels have been nominated as potential alloys for ultra-high strength and excellent ductility, but the high-Mn content inevitably generates band-shaped Mn-segregation due to dendritic solidification from the steel melt. This segregation band often causes unintended deformation mechanisms and anisotropic mechanical properties, and deteriorates formability. Here, we effectively utilize the Mn-segregated bands for the improvement of tensile properties by actively producing TWinning- and TRansformation-induced plasticity (TWIP and TRIP) mechanisms in high- and low-Mn-segregated bands. We also adopt a mixed microstructure of non-recrystallized and recrystallized austenite mainly formed in high- and low-Mn-segregated bands, respectively. The TWIP+TRIP mechanisms generating highly-sustained strain hardening and high strain hardening, coupled with partial recrystallization and precipitation hardening, are working successfully for overcoming low-yield-strength characteristics of austenite to reach 1 GPa and for achieving the excellent tensile strength of 1.5 GPa and ductility of 44%. Our results demonstrate how the Mn-segregation-induced TWIP+TRIP mechanisms can be a novel idea in ultra-high-strength steel design.

Original language	English
Pages (from-to)	69-76
Number of pages	8
Journal	Materials Science and Engineering A
Volume	737
DOIs	https://doi.org/10.1016/j.msea.2018.09.024
Publication status	Published - 2018 Nov 8
Externally published	Yes

Keywords

Austenitic steel
Mechanical properties
Mn-segregation
Recrystallization
TRIP and TWIP mechanisms

ASJC Scopus subject areas

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

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10.1016/j.msea.2018.09.024

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Exceptional combination of ultra-high strength and excellent ductility by inevitably generated Mn-segregation in austenitic steel. / Jo, Min Chul; Lee, Hyungsoo; Zargaran, A.; Ryu, Joo Hyun; Sohn, Seok Su; Kim, Nack J.; Lee, Sunghak.

In: Materials Science and Engineering A, Vol. 737, 08.11.2018, p. 69-76.

Research output: Contribution to journal › Article › peer-review

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title = "Exceptional combination of ultra-high strength and excellent ductility by inevitably generated Mn-segregation in austenitic steel",

abstract = "Austenitic high-Mn steels have been nominated as potential alloys for ultra-high strength and excellent ductility, but the high-Mn content inevitably generates band-shaped Mn-segregation due to dendritic solidification from the steel melt. This segregation band often causes unintended deformation mechanisms and anisotropic mechanical properties, and deteriorates formability. Here, we effectively utilize the Mn-segregated bands for the improvement of tensile properties by actively producing TWinning- and TRansformation-induced plasticity (TWIP and TRIP) mechanisms in high- and low-Mn-segregated bands. We also adopt a mixed microstructure of non-recrystallized and recrystallized austenite mainly formed in high- and low-Mn-segregated bands, respectively. The TWIP+TRIP mechanisms generating highly-sustained strain hardening and high strain hardening, coupled with partial recrystallization and precipitation hardening, are working successfully for overcoming low-yield-strength characteristics of austenite to reach 1 GPa and for achieving the excellent tensile strength of 1.5 GPa and ductility of 44%. Our results demonstrate how the Mn-segregation-induced TWIP+TRIP mechanisms can be a novel idea in ultra-high-strength steel design.",

keywords = "Austenitic steel, Mechanical properties, Mn-segregation, Recrystallization, TRIP and TWIP mechanisms",

author = "Jo, {Min Chul} and Hyungsoo Lee and A. Zargaran and Ryu, {Joo Hyun} and Sohn, {Seok Su} and Kim, {Nack J.} and Sunghak Lee",

note = "Funding Information: This work was supported by POSCO (Pohang Iron and Steel Company) under a contract No. 2016Y029 and by Brain Korea 21 PLUS Project for Center for Creative Industrial Materials. S.S. Sohn is grateful to the kind support of the Alexander von Humboldt Stiftung (AvH, Alexander von Humboldt Foundation, https://www.humboldt –foundation.de). Publisher Copyright: {\textcopyright} 2018 Elsevier B.V. Copyright: Copyright 2018 Elsevier B.V., All rights reserved.",

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doi = "10.1016/j.msea.2018.09.024",

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AU - Jo, Min Chul

AU - Lee, Hyungsoo

AU - Zargaran, A.

AU - Ryu, Joo Hyun

AU - Sohn, Seok Su

AU - Kim, Nack J.

AU - Lee, Sunghak

N1 - Funding Information: This work was supported by POSCO (Pohang Iron and Steel Company) under a contract No. 2016Y029 and by Brain Korea 21 PLUS Project for Center for Creative Industrial Materials. S.S. Sohn is grateful to the kind support of the Alexander von Humboldt Stiftung (AvH, Alexander von Humboldt Foundation, https://www.humboldt –foundation.de). Publisher Copyright: © 2018 Elsevier B.V. Copyright: Copyright 2018 Elsevier B.V., All rights reserved.

PY - 2018/11/8

Y1 - 2018/11/8

N2 - Austenitic high-Mn steels have been nominated as potential alloys for ultra-high strength and excellent ductility, but the high-Mn content inevitably generates band-shaped Mn-segregation due to dendritic solidification from the steel melt. This segregation band often causes unintended deformation mechanisms and anisotropic mechanical properties, and deteriorates formability. Here, we effectively utilize the Mn-segregated bands for the improvement of tensile properties by actively producing TWinning- and TRansformation-induced plasticity (TWIP and TRIP) mechanisms in high- and low-Mn-segregated bands. We also adopt a mixed microstructure of non-recrystallized and recrystallized austenite mainly formed in high- and low-Mn-segregated bands, respectively. The TWIP+TRIP mechanisms generating highly-sustained strain hardening and high strain hardening, coupled with partial recrystallization and precipitation hardening, are working successfully for overcoming low-yield-strength characteristics of austenite to reach 1 GPa and for achieving the excellent tensile strength of 1.5 GPa and ductility of 44%. Our results demonstrate how the Mn-segregation-induced TWIP+TRIP mechanisms can be a novel idea in ultra-high-strength steel design.

AB - Austenitic high-Mn steels have been nominated as potential alloys for ultra-high strength and excellent ductility, but the high-Mn content inevitably generates band-shaped Mn-segregation due to dendritic solidification from the steel melt. This segregation band often causes unintended deformation mechanisms and anisotropic mechanical properties, and deteriorates formability. Here, we effectively utilize the Mn-segregated bands for the improvement of tensile properties by actively producing TWinning- and TRansformation-induced plasticity (TWIP and TRIP) mechanisms in high- and low-Mn-segregated bands. We also adopt a mixed microstructure of non-recrystallized and recrystallized austenite mainly formed in high- and low-Mn-segregated bands, respectively. The TWIP+TRIP mechanisms generating highly-sustained strain hardening and high strain hardening, coupled with partial recrystallization and precipitation hardening, are working successfully for overcoming low-yield-strength characteristics of austenite to reach 1 GPa and for achieving the excellent tensile strength of 1.5 GPa and ductility of 44%. Our results demonstrate how the Mn-segregation-induced TWIP+TRIP mechanisms can be a novel idea in ultra-high-strength steel design.

KW - Austenitic steel

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KW - Mn-segregation

KW - Recrystallization

KW - TRIP and TWIP mechanisms

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SN - 0921-5093

ER -

Exceptional combination of ultra-high strength and excellent ductility by inevitably generated Mn-segregation in austenitic steel

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