Tuning nanostructure using thermo-mechanical processing for enhancing mechanical properties of complex intermetallic containing CoCrFeNi2.1Nbx high entropy alloys

Tuning nanostructure using thermo-mechanical processing for enhancing mechanical properties of complex intermetallic containing CoCrFeNi2.1Nbx high entropy alloys

Possibilities of tailoring microstructure and mechanical properties of complex intermetallic containing CoCrFeNi2.1Nbx (x = 0.2, 0.4) high entropy alloys (HEAs) using thermo-mechanical processing were investigated in this work. For this purpose, the homogenized HEAs containing complex Laves phases d...

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Bibliographic Details
Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 769; p. 138489
Main Authors: Sunkari, U., Reddy, S.R., Rathod, B.D.S., Kumar, D., Saha, R., Chatterjee, S., Bhattacharjee, P.P.
Format: Journal Article
Language:English
Published: Lausanne Elsevier B.V 02-01-2020
Elsevier BV
Subjects:
Annealing
Cold rolling
Deformation
Ductility
Elongation
Grain refinement
Grain size
High entropy alloys
Intermetallic phases
Intermetallics
Laves phase
Mechanical properties
Microstructure
Nucleation
Precipitates
Precipitation hardening
Recrystallization
Rolling direction
Tensile strength
Thermomechanical treatment
High entropy alloys
Intermetallics
Mechanical properties
Cold-rolling
Microstructure
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Summary:Possibilities of tailoring microstructure and mechanical properties of complex intermetallic containing CoCrFeNi2.1Nbx (x = 0.2, 0.4) high entropy alloys (HEAs) using thermo-mechanical processing were investigated in this work. For this purpose, the homogenized HEAs containing complex Laves phases distributed in the FCC matrix were successfully severely cold-rolled up to 90% reduction in thickness. The cold-rolled HEAs showed a nano lamellar microstructure with fragmented Laves phase particles arranged preferentially along the rolling direction. The microstructure of the Nb0.4 HEA revealed intense deformation zones surrounding the hard Laves phase particles, owing to their higher volume fraction and larger size as compared to those in the Nb0.2 HEA. Upon annealing at 800 °C, the lamellar deformed FCC phase in the two HEAs was transformed into an equiaxed nano-grained structure having fine dispersion of nano precipitates. However, the Nb0.4 showed a decidedly lower recrystallized grain size than the Nb0.2, resulting from the smaller deformed grain size and particle stimulated nucleation. The annealed Nb0.2 showed remarkable strength-ductility combination featured by tensile strength ~1080 MPa and ductility ~21%, originating from the combined effect of a high volume of ductile FCC matrix, remarkable grain refinement, and precipitation hardening. In stark contrast, the annealed Nb0.4 showed complete absence of tensile elongation, likely due to a low volume fraction of the ductile FCC matrix and a high volume fraction of the intermetallic phases. The present study emphasized the critical role of microstructural tailoring for achieving outstanding strength-ductility synergy in complex intermetallic containing CoCrFeNi2.1Nbx HEAs.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2019.138489