Simultaneous enhancement of strength and ductility via microband formation and nanotwinning in an L12-strengthened alloy

Lu Yang, Dingshan Liang, Zhuo Cheng, Ranxi Duan, Chuanxin Zhong, Junhua Luan, Zengbao Jiao, Fuzeng Ren

Research output: Journal article publicationJournal articleAcademic researchpeer-review

Abstract

Metallic alloys with high strength and large ductility are required for extreme structural applications. However, the achievement of ultrahigh strength often results in a substantially decreased ductility. Here, we report a strategy to achieve the strength-ductility synergy by tailoring the alloy composition to control the local stacking fault energy (SFE) of the face-centered-cubic (fcc) matrix in an L12-strengthened superlattice alloy. As a proof of concept, based on the thermodynamic calculations, we developed a non-equiatomic CoCrNi2(Al0.2Nb0.2) alloy using phase separation to create a near-equiatomic low SFE disordered CoCrNi medium-entropy alloy matrix with in situ formed high-content coherent Ni3(Al, Nb)-type ordered nanoprecipitates (∼ 12 nm). The alloy achieves a high tensile strength up to 1.6 GPa and a uniform ductility of 33%. The low SFE of the fcc matrix promotes the formation of nanotwins and parallel microbands during plastic deformation which could remarkably enhance the strain hardening capacity. This work provides a strategy for developing ultrahigh-strength alloys with large uniform ductility.

Original languageEnglish
JournalFundamental Research
DOIs
Publication statusAccepted/In press - 2022

Keywords

  • L1-strengthened superlattice alloy
  • Microbands
  • Nanotwins
  • Stacking fault energy
  • Strain hardening

ASJC Scopus subject areas

  • General

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