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 S Sohn, Nack J. Kim, Sunghak Lee

Research output: Contribution to journalArticle

4 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 languageEnglish
Pages (from-to)69-76
Number of pages8
JournalMaterials Science and Engineering A
Volume737
DOIs
Publication statusPublished - 2018 Nov 8
Externally publishedYes

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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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