Gradient nanotwinned CrCoNi medium-entropy alloy with strength-ductility synergy

Shuqing Yuan, Bin Gan, Lei Qian, Bo Wu, Hui Fu, Hong Hui Wu, Chi Fai Cheung, Xu Sheng Yang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

36 Citations (Scopus)


In this study, a high-strain rate ultra-precision machining technology named single point cubic boron nitride turning is developed to fabricate a gradient nanotwinned CrCoNi medium entropy alloy layer. The grain size of the ~ 150 µm-thick gradient layer is gradually refined from the original ~ 17 µm to ~ 25 nm in the topmost surface, exhibiting a significantly enhanced yield strength (from ~ 450 MPa to ~ 1100 MPa) and well-retained ductility of ~ 27%. High-resolution transmission electron microscope and atomistic simulations were mainly performed to unveil the size-dependent twinning mechanisms governing the gradient refinement process from the core to the topmost surface, i.e. transiting from the parallel twins segmenting ultrafine grains, twin-twin intersections refining rhombic blocks and rotating the intersected nanograins, and finally to the zero-macrostrain deformation nanotwinning in the refined nanograins. The machining process provides sufficient equivalent stress to activate the twinning partials for forming the gradient nanotwinned structure.

Original languageEnglish
Article number114117
JournalScripta Materialia
Publication statusPublished - Oct 2021


  • Gradient nanotwinned structure
  • High-resolution transmission electron microscope
  • Medium-entropy alloy
  • Twin-twin intersection
  • Ultra-precision machining technology

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys


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