Probing deformation mechanisms of a FeCoCrNi high-entropy alloy at 293 and 77 K using in situ neutron diffraction

Research output: Contribution to journalArticle

Authors

  • Yiqiang Wang
  • Bin Liu
  • Kun Yan
  • Saurabh Kabra
  • David Dye
  • Peter D. Lee
  • Yong Liu

Colleges, School and Institutes

External organisations

  • Culham Centre for Fusion Energy, Culham Science Centre
  • Research Complex at Harwell
  • The State Key Laboratory of Powder Metallurgy, Central South University
  • Imperial College London
  • ISIS Facility, Rutherford Appleton Laboratory
  • State Key Laboratory of Powder Metallurgy
  • Central South University China

Abstract

The deformation responses at 77 and 293 K of a FeCoNiCr high-entropy alloy, produced by a powder metallurgy route, are investigated using in situ neutron diffraction and correlative transmission electron microscopy. The strength and ductility of the alloy are significant improved at cryogenic temperatures. The true ultimate tensile strength and total elongation increased from 980 MPa and 45% at 293 K to 1725 MPa and 55% at 77K, respectively. The evolutions of lattice strain, stacking fault probability, and dislocation density were determined via quantifying the in situ neutron diffraction measurements. The results demonstrate that the alloy has a much higher tendency to form stacking faults and mechanical twins as the deformation temperature drops, which is due to the decrease of stacking fault energy (estimated to be 32.5 mJ/m2 and 13 mJ/m2 at 293 and 77 K, respectively). The increased volume faction of nano-twins and twin-twin intersections, formed during cryogenic temperature deformation, has been confirmed by transmission electron microscopy analysis. The enhanced strength and ductility at cryogenic temperatures can be attributed to the increased density of dislocations and nano-twins. The findings provide a fundamental understanding of underlying governing mechanistic mechanisms for the twinning induced plasticity in high entropy alloys, paving the way for the development of new alloys with superb resistance to cryogenic environments.

Details

Original languageEnglish
Article numberA-18-91R1
JournalActa Materialia
Early online date10 May 2018
Publication statusPublished - 1 Aug 2018

Keywords

  • high entropy alloy , deformation twinning , neutron diffraction , cryogenic deformation , stacking fault energy