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Effect of Cr and Al on phase constitution and high temperature oxidation behavior of Al-Co-Cr-Fe-Ni high entropy alloys

Bhattacharya, Rahul LU (2023)
Abstract
In this thesis, the inherent oxidation resistance of Al-Co-Cr-Fe-Ni based high entropy alloys have been remarkably enhanced by increasing the grain boundary area and recognizing the influence of the in situ Al2O3 nano-dispersoids. Isothermal continuous oxidation test based on thermogravimetric analysis (TGA) as well as extensive furnace oxidation, were conducted in the elevated temperature range of 850-1150℃ (1 atm) for 5-200h duration to investigate the
thermodynamical driving force and kinetics associated with various stages of oxidation.

According to Ellingham diagrams, Al followed by Cr have the highest affinity towards oxygen in the temperature and pressure range discussed above.
Nine HEA compositions based on... (More)
In this thesis, the inherent oxidation resistance of Al-Co-Cr-Fe-Ni based high entropy alloys have been remarkably enhanced by increasing the grain boundary area and recognizing the influence of the in situ Al2O3 nano-dispersoids. Isothermal continuous oxidation test based on thermogravimetric analysis (TGA) as well as extensive furnace oxidation, were conducted in the elevated temperature range of 850-1150℃ (1 atm) for 5-200h duration to investigate the
thermodynamical driving force and kinetics associated with various stages of oxidation.

According to Ellingham diagrams, Al followed by Cr have the highest affinity towards oxygen in the temperature and pressure range discussed above.
Nine HEA compositions based on Al-Co-Cr-Fe-Ni system were synthesized by
systematically varying the nominal content of Al and Cr. These nine HEAs have been recognized into three groups based on Al or Cr variation viz. equiatomic HEAs (CoCrFeNi, AlCoFeNi, and AlCoCrFeNi), non-equiatomic Cr-variation HEAs (AlCoCr0.25FeNi, AlCoCr0.50FeNi, and AlCoCr0.75FeNi), as well as non-equiatomic Al-variation HEAs (Al0.25CoCrFeNi, Al0.50CoCrFeNi, and Al0.75CoCrFeNi). (Less)
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author
supervisor
publishing date
type
Thesis
publication status
published
subject
keywords
Al-Co-Cr-Fe-Ni Based HEAs, Mechanical alloying, Spark plasma sintering, Bimodal grain size distribution, Process optimization, Grain boundary efect
pages
285 pages
language
English
LU publication?
no
additional info
Joint doctoral program (JDP): IIT Madras-Deakin University, Australia JDP Received Res-part scholarship and conducted the high temperature oxidation as well as elaborate post-oxidation characterization section of Thesis research in collaboration with Institute for Frontier Materials at Deakin University under the supervision of Prof. Daniel Fabijanic. The alloy design and process design were entirely conducted at the Department of MME at IIT Madras under the supervision of Prof. B. S. Murty (Director IIT Hyderabad).
id
8a4fa4ad-0268-49d1-8d43-e0078614e5a3
date added to LUP
2025-08-31 12:16:11
date last changed
2025-09-22 16:30:39
@phdthesis{8a4fa4ad-0268-49d1-8d43-e0078614e5a3,
  abstract     = {{In this thesis, the inherent oxidation resistance of Al-Co-Cr-Fe-Ni based high entropy alloys have been remarkably enhanced by increasing the grain boundary area and recognizing the influence of the in situ Al2O3 nano-dispersoids. Isothermal continuous oxidation test based on thermogravimetric analysis (TGA) as well as extensive furnace oxidation, were conducted in the elevated temperature range of 850-1150℃ (1 atm) for 5-200h duration to investigate the<br/>thermodynamical driving force and kinetics associated with various stages of oxidation.<br/><br/>According to Ellingham diagrams, Al followed by Cr have the highest affinity towards oxygen in the temperature and pressure range discussed above.<br/>Nine HEA compositions based on Al-Co-Cr-Fe-Ni system were synthesized by<br/>systematically varying the nominal content of Al and Cr. These nine HEAs have been recognized into three groups based on Al or Cr variation viz. equiatomic HEAs (CoCrFeNi, AlCoFeNi, and AlCoCrFeNi), non-equiatomic Cr-variation HEAs (AlCoCr0.25FeNi, AlCoCr0.50FeNi, and AlCoCr0.75FeNi), as well as non-equiatomic Al-variation HEAs (Al0.25CoCrFeNi, Al0.50CoCrFeNi, and Al0.75CoCrFeNi).}},
  author       = {{Bhattacharya, Rahul}},
  keywords     = {{Al-Co-Cr-Fe-Ni Based HEAs; Mechanical alloying; Spark plasma sintering; Bimodal grain size distribution; Process optimization; Grain boundary efect}},
  language     = {{eng}},
  title        = {{Effect of Cr and Al on phase constitution and high temperature oxidation behavior of Al-Co-Cr-Fe-Ni high entropy alloys}},
  year         = {{2023}},
}