Strain partitioning enables excellent tensile ductility in precipitated heterogeneous high-entropy alloys with gigapascal yield strength

Feng He, Zhongsheng Yang, Shaofei Liu, Da Chen, Weitong Lin, Tao Yang, Daixiu Wei, Zhijun Wang, Jincheng Wang, Ji jung Kai

Research output: Contribution to journalArticlepeer-review

Abstract

High entropy alloys (HEAs) with grain-scale heterogeneous structure and coherent precipitates have shown gigapascal strength and considerable ductility. However, the origins of the excellent ductility of the HEAs with both precipitates and grain-scale heterogeneous structures are relatively less explored and not well understood. It is also still challenging to obtain such precipitated heterogeneous HEAs through efficient and economical thermomechanical processing procedures. Here, through single-step heat treatment, we developed a Ni2CoCrFeTi0.24Al0.2 HEA with an excellent yield strength of ~1.3 GPa and tensile elongation of ~20%. Using multiple length-scale microstructure characterizations and micro-digital image correlation analysis, we revealed the strengthening and toughening mechanisms of the novel HEA. Our results showed that the grain-scale heterogeneous structure with L12 precipitates ranging from ~10 to 100 nm is responsible for the excellent strength-ductility combination. The good ductility is attributed to the strain-partitioning-induced additional deformation modes, i.e., deformation twinning and microbands, as well as the efficient hetero-deformation induced strain hardening effect. The superior yield strength is mainly due to the effective combination of precipitation hardening and dislocation strengthening. These findings not only provide a facile route to develop strong and ductile alloys but also deepen the understanding of the deformation mechanism of hetero-structured materials.

Original languageEnglish
Article number103022
JournalInternational Journal of Plasticity
Volume144
DOIs
Publication statusPublished - 2021 Sep

Keywords

  • Deformation mechanism
  • Heterogeneous structure
  • High entropy alloys
  • Mechanical properties

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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