Multiscale defects enable synergetic improvement in yield strength of CrCoNi-based medium-entropy alloy fabricated via laser-powder bed fusion

Heechan Jung, Jungwan Lee, Gang Hee Gu, Hyungsoo Lee, Seong Moon Seo, Alireza Zargaran, Hyoung Seop Kim, Seok Su Sohn

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

Recently, laser-powder bed fusion (L-PBF) has overcome a shortcoming concerning the relatively modest yield strength in the face-centered cubic structure of CrCoNi medium-entropy alloy (MEA); nevertheless, further enhancement remains challenging because the as-built defects are limited to dislocation cell structures and nano-inclusions. In this study, several the types of hierarchical defect structures are explored (including stacking faults, nano-twins, σ phase, and nano-precipitates) with the addition of Si to reduce the stacking fault energy and promote segregation at dislocation cells with Cr. The CrCoNiSi0.3 alloy is fabricated by the L-PBF process, and the effects of the Si addition and L-PBF processing on the hierarchical multiscale defects and corresponding mechanical responses are unraveled. The highest apparent density above 99.5 % is achieved under optimized conditions, exhibiting a high yield strength of 929 MPa owing to a synergetic effect from the generated defects comprising σ phase, nano-twins, and planar defects with moderate ductility of 14 %. In addition, the reduced stacking fault energy promotes deformation twinning, resulting in steady strain hardening. The alloy ultimately exhibits a tensile strength of 1264 MPa, with a moderate ductility of 14 %. A post-heat treatment induces a morphological change in the σ phase from a film-type at the cell walls to particulates at the cell junctions, leading to a significant increase in ductility without a loss of tensile strength, despite a loss of yield strength. This work provides insights to overcome the pre-existing limitations by imposing and adjusting multiscale defects.

Original languageEnglish
Article number103360
JournalAdditive Manufacturing
Volume61
DOIs
Publication statusPublished - 2023 Jan 5

Bibliographical note

Funding Information:
This study was supported by the Korea TechnoComplex Foundation Grant [ R2214141 ]; the National Research Foundation of Korea (NRF) grant funded by the Korea government ( MSIT ) [ NRF-2022R1A5A1030054 ]; the Korea Institute for Advancement of Technology (KIAT) grant funded by the Korean Government ( MOTIE ) [ P0002019 , The Competency Development Program for Industry Specialist]; and the Fundamental Research Program of the Korean Institute of Materials Science [ PNK8730 ].

Publisher Copyright:
© 2022 Elsevier B.V.

Keywords

  • Additive manufacturing
  • Laser-powder bed fusion
  • Mechanical property
  • Multiscale defects
  • Segregation

ASJC Scopus subject areas

  • Biomedical Engineering
  • General Materials Science
  • Engineering (miscellaneous)
  • Industrial and Manufacturing Engineering

Fingerprint

Dive into the research topics of 'Multiscale defects enable synergetic improvement in yield strength of CrCoNi-based medium-entropy alloy fabricated via laser-powder bed fusion'. Together they form a unique fingerprint.

Cite this