Anisotropic plasticity mechanisms in a newly synthesised high entropy alloy investigated using atomic simulations and nanoindentation experiments

Pengfei Fan, Nirmal Kumar Katiyar, Muhammad Arshad, Mingwen Bai, Hui Mao, Saurav Goel

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1 Citation (Scopus)
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Abstract

This work used atomic simulations and nanoindentation experiments to investigate hardness, modulus alongside sub-surface crystal defects and dislocation mediated plasticity mechanisms leading to anisotropic pile up and local entropy variation in high entropy alloys. The experimental campaign began from Thermo-Calc phase prediction of Ni25Cu18.75Fe25Co25Al6.25 HEA which followed experimental synthesis of the material using arc melting method and experimental nanoindentation using a Berkovich indenter under load-controlled conditions. Through MD simulations, the value of hf/hmax in monocrystalline HEA was consistently found to be larger than 0.7 which suggested pile-up behaviour to dominate and sink-in behaviour to be unlikely. In the case of (110) and polycrystalline HEA substrates, the elastic work in the indentation hysteresis loop was seen to be larger than the (100) and the (111) orientations which explains that the (110) orientation substrate showed least elastic modulus and hardness while the (111) monocrystalline HEA showed the highest elastic modulus and hardness. From the simulations, a “lasso” type loop on the (110) orientation and cross-over of shear loops on the other orientations accompanied by dislocations of type 1/6 < 112 > (Shockley), 1/2 < 110 > (perfect), 1/3 < 001 > (Hirth), 1/6 < 110 > (Stair rod) and 1/3 < 111 > (Frank partials) were seen to manifest an early avalanche of competing plasticity events. The defects accompanying these dislocations in the sub-surface were identified to be FCC intrinsic stacking faults (ISF), adjacent intrinsic stacking faults (quad faults), coherent ∑3 twin boundary and a coherent twin boundary next to an intrinsic stacking fault (triple fault). The EBSD analysis applied to the MD data showed that the (210) orientation and the< 110 > family of directions were seemed to be preferable to plastically deform the FCC phased Ni25Cu18.75Fe25Co25Al6.25 HEA.

Original languageEnglish
Article number172541
Number of pages14
JournalJournal of Alloys and Compounds
Volume970
Early online date16 Oct 2023
DOIs
Publication statusPublished - 5 Jan 2024

Bibliographical note

This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Funder

SG would like to acknowledge the financial support provided by the UKRI via Grants No. EP/S036180/1 and EP/T024607/1, Hubert Curien Partnership Programme from the British Council and the International Exchange Cost Share award by the Royal Society (IEC\NSFC\223536). This work also accessed the Isambard Bristol, UK supercomputing service via Resource Allocation Panel (RAP), Kittrick HPC at LSBU and Param Kamrupa HPC based at Guwahati, India.

Keywords

  • High entropy alloy
  • Deformation behaviour
  • Grain boundaries
  • Nanoindentation
  • MD simulations

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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