Effects of Mn Segregations on Intergranular Fracture in a Medium-Mn Low-Density Steel

Heechan Jung, Gunjick Lee, Minseo Koo, Hyejin Song, Won Seok Ko, Seok Su Sohn

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Al-bearing medium-Mn low-density steels possess great potential in the automotive industry because of their excellent mechanical properties based on transformation-induced plasticity and low specific weight. Reducing the austenite stability against deformation-induced martensitic transformation enables a high strain-hardening capacity to be obtained; however, undesirably low stability often results in considerably reduced tensile ductility and brittle fracture. Herein, the brittle fracture that occurs with increasing annealing temperature for a Fe−0.3C–9Mn−5Al (wt%) steel is investigated in relation to Mn segregation at the phase boundaries between ferrite and austenite. The results demonstrate that annealing at 850 and 900 °C leads to ductile fractures with 72% and 95% tensile elongation, respectively, whereas only 25% elongation is achieved for the specimen annealed at 950 °C, exhibiting predominant intergranular facets. 3D atom probe tomography reveals that annealing at 950 °C promotes considerable Mn segregation at the ferrite/austenite phase boundaries with a peak composition of ≈19 at%, which is sufficient to reduce the boundary cohesion for intergranular fracture. Thermodynamic moving boundary simulation reveals that intercritical annealing is not a prerequisite for segregations; however, low-temperature and prolonged holding should be accompanied, such as the coiling procedures.

Original languageEnglish
Article number2200240
JournalSteel Research International
Volume94
Issue number2
DOIs
Publication statusPublished - 2023 Feb

Bibliographical note

Funding Information:
This work was supported by Korea Institute for Advancement of Technology (KIAT) grant funded by the Korea Government (MOTIE) (P0002019, The Competency Development Program for Industry Specialist) and by Fundamental Research Program of the Korean Institute of Materials Science (PNK8730).

Publisher Copyright:
© 2022 Wiley-VCH GmbH.

Keywords

  • atom probe tomography
  • intergranular fractures
  • low-density steels
  • segregations

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Metals and Alloys
  • Materials Chemistry

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