Defect structure and hardness in nanocrystalline CoCrFeMnNi High-Entropy Alloy processed by High-Pressure Torsion

Anita Heczel, Megumi Kawasaki, János L. Lábár, Jae il Jang, Terence G. Langdon, Jenő Gubicza

Research output: Contribution to journalArticle

37 Scopus citations

Abstract

An equiatomic CoCrFeMnNi High-Entropy Alloy (HEA) produced by arc melting was processed by High-Pressure Torsion (HPT). The evolution of the microstructure during HPT was investigated after ¼, ½, 1 and 2 turns using electron backscatter diffraction and transmission electron microscopy. The spatial distribution of constituents was studied by energy-dispersive X-ray spectroscopy. The dislocation density and the twin-fault probability in the HPT-processed samples were determined by X-ray line profiles analysis. It was found that the grain size was gradually refined from ∼60 μm to ∼30 nm while the dislocation density and the twin-fault probability increased to very high values of about 194 × 1014 m−2 and 2.7%, respectively, at the periphery of the disk processed for 2 turns. The hardness evolution was measured as a function of the distance from the center of the HPT-processed disks. After 2 turns of HPT, the microhardness increased from ∼1440 MPa to ∼5380 MPa at the disk periphery where the highest straining is achieved. The yield strength was estimated as one-third of the hardness and correlated to the microstructure.

Original languageEnglish
Pages (from-to)143-154
Number of pages12
JournalJournal of Alloys and Compounds
Volume711
DOIs
StatePublished - 2017 Jan 1

Keywords

  • Dislocations
  • Hardness
  • High-Entropy Alloy
  • High-Pressure Torsion
  • Twin faults
  • X-ray diffraction

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