Utilization of brittle σ phase for strengthening and strain hardening in ductile VCrFeNi high-entropy alloy

Y. H. Jo, W. M. Choi, D. G. Kim, A. Zargaran, K. Lee, H. Sung, Seok S Sohn, H. S. Kim, B. J. Lee, S. Lee

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

General design concept used in high-entropy alloys (HEAs) have deviated from forming an fcc single phase to utilizing hard intermetallic phases in ductile fcc matrix. Here, we effectively exploited strengthening effects of a brittle intermetallic sigma (σ) phase to improve cryogenic tensile properties of a non-equi-atomic ductile VCrFeNi four-component HEA. We preferentially selected vanadium as a candidate alloying element to efficiently produce the σ phase through computational thermodynamic approach. This σ phase has beneficial effects on grain refinement through retardation of grain growth due to grain-boundary pinning, thereby leading to yield strength of 0.79–0.93 GPa. The extensive strain hardening results in tensile strength of 1.33–1.49 GPa and ductility of 23–47% at cryogenic temperature, which are enabled by nano-sized dislocation substructures rather than deformation twinning. Our results demonstrate how the intermetallic σ phase, which has been avoided in typical HEAs because of ductility deterioration, could be used in high strength HEA design.

Original languageEnglish
Pages (from-to)665-674
Number of pages10
JournalMaterials Science and Engineering A
Volume743
DOIs
Publication statusPublished - 2019 Jan 16
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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