Hydrogen diffusivity and interaction with Fe20Mn20Ni20Co20Cr20 and Fe22Mn40Ni30Co6Cr2 high-entropy alloys

The Equimolar Fe20Mn20Ni20Co20Cr20 and non-equimolar, Fe22Mn40Ni30Co6Cr2, high-entropy alloys were synthesized and characterized in the present work. Cold rolled and heat-treated samples were studied via scanning electron microscopy, SEM, atomic force microscopy, AFM and X-ray diffraction, XRD. The...

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Bibliographic Details
Published in:	Journal of alloys and compounds Vol. 815; p. 152314
Main Authors:	Belo, J.S., Marques, S.C., Castilho, A.V., de Oliveira, L.M., Simão, R.A., dos Santos, D.S.
Format:	Journal Article
Language:	English
Published:	Lausanne Elsevier B.V 30-01-2020 Elsevier BV
Subjects:	Atomic force microscopy Austenitic stainless steels Cold rolling Cold working Cubic lattice Density functional theory Diffusion rate Diffusivity First principles Gas permeation Heat treatment High entropy alloys High pressure torsion Hydrogen Hydrogen diffusivity Hydrogen permeation Microscopy Penetration Phase equilibria Plastic deformation Sigma phase Solidification Thermodynamic equilibrium High entropy alloys First principles Hydrogen diffusivity High pressure torsion
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Summary:	The Equimolar Fe20Mn20Ni20Co20Cr20 and non-equimolar, Fe22Mn40Ni30Co6Cr2, high-entropy alloys were synthesized and characterized in the present work. Cold rolled and heat-treated samples were studied via scanning electron microscopy, SEM, atomic force microscopy, AFM and X-ray diffraction, XRD. The equimolar alloy was submitted to severe plastic deformation by high-pressure torsion, HPT. Hydrogen permeation of both alloys under all conditions were measured by gas permeation tests. It was observed that the hydrogen diffusivity of all samples at 300 °C, are in the same order of magnitude as the ones for austenitic stainless steels. The HPT deformed sample presented the highest hydrogen diffusivity, in comparison with cold worked sample, suggesting fast diffusion through the refined microstructure. Thermocalc® results predict the presence of sigma-phase during solidification of theses alloys. Density-functional theory, DFT, thermodynamic simulations of phase equilibria and first-principles, were performed for both alloys where a small distortion of cubic lattice for both compositions, with the equimolar system presenting the lowest total energy obtained by DFT. •Hydrogen diffusivity in high entropy alloys.•First principles simulation of high entropy alloys.•High entropy alloy Microstructure interaction with hydrogen.
ISSN:	0925-8388 1873-4669
DOI:	10.1016/j.jallcom.2019.152314