University of Oulu

Patnamsetty, M., Somani, M. C., Ghosh, S., Ahmed, S., & Peura, P. (2020). Processing map for controlling microstructure and unraveling various deformation mechanisms during hot working of CoCrFeMnNi high entropy alloy. Materials Science and Engineering: A, 793, 139840. https://doi.org/10.1016/j.msea.2020.139840

Processing map for controlling microstructure and unraveling various deformation mechanisms during hot working of CoCrFeMnNi high entropy alloy

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Author: Patnamsetty, Madan1; Somani, Mahesh2; Ghosh, Sumit2;
Organizations: 1Materials Science and Environmental Engineering, Tampere University, 33720, Tampere, Finland
2Materials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, 90014, Finland
Format: article
Version: accepted version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe2022021719709
Language: English
Published: Elsevier, 2020
Publish Date: 2022-07-03
Description:

Abstract

In the current study, the hot deformation characteristics and workability of a CoCrFeMnNi high entropy alloy was characterized using processing maps developed on the basis of dynamic materials model in the temperature range 1023–1423 K and strain rate range 10⁻³–10s⁻¹. The processing map delineated various deterministic domains including those of cracking processes and unstable flow, thus enabling identification of a ‘safe’ processing window for the hot working of the alloy. Accordingly, a deterministic domain in the temperature and strain rate ranges of 1223–1373 K and 10⁻²–5 × 10⁻¹s⁻¹, respectively, was identified to be the domain of dynamic recrystallization (DRX) with a peak efficiency of the order of ~34% at 1293 K and 3 × 10⁻²s⁻¹ and these were considered to be the optimum parameters for hot deformation. The DRX grain size was dependent on the deformation temperature and strain rate, increasing with the increase in temperature and decrease in strain rate, whereas DRX volume increased with the strain rate. At still higher temperatures (1403–1423 K) and lower strain rates (10⁻³–3 × 10⁻³s⁻¹), there was a sharp decrease in efficiency values from 27% to 5% thus forming a trough and the microstructure was characterized with coarse grains. In the instability regime, grain boundary cracking/sliding and localized shear bands manifested at temperatures <1223 K and strain rates <10⁻²s⁻¹. The increase in strain rate resulted in an intense adiabatic shear banding along with formation of voids. At 10s⁻¹ and temperatures >1398 K, microstructural reconstitution occurred in the shear bands leading to the formation of fine grains, presumably as a consequence of continuous recrystallization.

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Series: Materials science & engineering. A, Structural materials: properties, microstructure and processing
ISSN: 0921-5093
ISSN-E: 1873-4936
ISSN-L: 0921-5093
Volume: 793
Article number: 139840
DOI: 10.1016/j.msea.2020.139840
OADOI: https://oadoi.org/10.1016/j.msea.2020.139840
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Subjects:
Funding: This study was performed with the support of Tampere University Foundation as a part of Tampere university graduate school.
Copyright information: © 2020 Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/.
  https://creativecommons.org/licenses/by-nc-nd/4.0/