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Grain growth kinetics in CoCrFeNi and CoCrFeMnNi high entropy alloys processed by spark plasma sintering

Vaidya, M and Anupam, Ameey and Bharadwaj, J Vijay and Srivastava, Chandan and Murty, B S (2019) Grain growth kinetics in CoCrFeNi and CoCrFeMnNi high entropy alloys processed by spark plasma sintering. In: JOURNAL OF ALLOYS AND COMPOUNDS, 791 . pp. 1114-1121.

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Official URL: https://dx.doi.org/10.1016/j.jallcom.2019.03.341

Abstract

Nanocrystalline CoCrFeNi and CoCrFeMnNi high entropy alloys have been processed by mechanical alloying followed by spark plasma sintering. Grain growth kinetics has been estimated for both the alloys by subjecting them to heat treatment in the temperature range 1073-1373 K. These alloys possess a thermally stable single phase FCC structure along with Cr7C3 contamination. Electron back scattered diffraction (EBSD) has been used to determine grain size of all the heat treated samples. Both CoCrFeNi and CoCrFeMnNi alloys exhibit a grain growth exponent, n=3, suggesting long-range diffusion controlled grain growth in these alloys. Activation energies for grain growth are 134 and 197 kJ/mol for CoCrFeNi and CoCrFeMnNi, respectively, which are significantly lower than the activation energy of lattice diffusion in these alloys. Hardness is measured for CoCrFeMnNi alloy as function of grain size and is found to follow the Hall-Petch type relation. The strength coefficient (slope of Hall-Petch relation) is calculated as 1.92 GPa, which is nearly three times that of the value reported in literature for coarse grained CoCrFeMnNi. Presence of carbides enhances the hardness of these HEAs. The maximum contribution to strengthening comes from the FCC-carbide phase boundaries.

Item Type: Journal Article
Additional Information: The copyright for this article belongs to Elsevier Ltd
Keywords: High entropy alloys; Grain growth; Activation energy; Hall-Petch; hardness
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Depositing User: Ms R.S. Ranganayaki
Date Deposited: 22 May 2019 12:23
Last Modified: 22 May 2019 12:23
URI: http://eprints.iisc.ac.in/id/eprint/62644

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