Role of brittle sigma phase in cryogenic-temperature-strength improvement of non-equi-atomic Fe-rich VCrMnFeCoNi high entropy alloys

Yong Hee Jo, Won Mi Choi, Seok S Sohn, Hyoung Seop Kim, Byeong Joo Lee, Sunghak Lee

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

An equi-atomic single-fcc-phase CrMnFeCoNi high entropy alloy (HEA) shows much higher tensile properties at cryogenic temperature than at room temperature because of its fcc characteristics and abundant twinning at cryogenic temperature. In order to further improve the cryogenic-temperature tensile properties of single-fcc-phase HEAs, we propose non-equi-atomic Fe-rich VCrMnFeCoNi HEAs, and analyze the strengthening effects of the brittle intermetallic sigma (σ) phase. The σ phase is unintentionally obtained, but favorably shows a pronounced strengthening by its hardness and grain refinement effect due to grain-boundary pinning, which leads to high yield and tensile strengths of 0.76 GPa and 1.23 GPa, respectively, together with good ductility of 54%. This positive utilization of the σ phase is unexpected because its formation has been suppressed in typical HEAs. Our results demonstrate that the present Fe-rich VCrMnFeCoNi design and σ-phase strengthening has potential in high-strength HEA studies.

Original languageEnglish
Pages (from-to)403-410
Number of pages8
JournalMaterials Science and Engineering A
Volume724
DOIs
Publication statusPublished - 2018 May 2
Externally publishedYes

Keywords

  • Cryogenic
  • High entropy alloy
  • Mechanical property
  • Sigma phase
  • Thermodynamic calculation

ASJC Scopus subject areas

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

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