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

Publication date: Available online 19 September 2019Source: Journal of Alloys and CompoundsAuthor(s): J. Belo, S.C. Marques, A.V. Castilho, L.M. de Oliveira, R.A. Simão, D.S. dos SantosAbstractThe 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.

Source: Journal of Alloys and Compounds - September 21, 2019 Category: Chemistry Source Type: research