Strain-Induced Lattice Distortions of a Hydrogenated Palladium-Based Alloy
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CTURE AND PROPERTIES OF THE DEFORMED STATE
Strain-Induced Lattice Distortions of a Hydrogenated Palladium-Based Alloy O. V. Akimovaa, *, A. A. Veligzhaninb, R. D. Svetogorovb, S. V. Gorbunovc, N. R. Roshanc, and G. S. Burkhanovc a
Faculty of Physics, Moscow State University, Moscow, 119991 Russia Research Centre Kurchatov Institute, Moscow, 123098 Russia c Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Moscow, 119334 Russia *e-mail: [email protected] bNational
Received February 6, 2020; revised February 27, 2020; accepted March 2, 2020
Abstract—The structural state of diffusive membrane filters made from a Pd94Y6 alloy, which have undergone a prolonged relaxation after hydrogenation, is studied. The phase composition and structure dispersity are determined. One of the membranes was subjected to secondary hydrogenation, and the effect of occluded hydrogen on the strain processes in the crystal lattice of the inhomogeneous material was demonstrated. High-resolution scanning electron microscopy is used to study the Ostwald ripening of the surface structure of the diffusion membrane filters after secondary hydrogenation. The fact of grain coalescence of an island structure, which can substantially affect the strength characteristics of the membranes, is found. Keywords: crystal lattice dilatation, hydrogen, palladium-based alloys, X-ray diffraction DOI: 10.1134/S003602952010002X
INTRODUCTION The effect of hydrogen on the structure and structure-sensitive properties of metals and alloys has long been known [1–3]; however, to date, the fundamental aspects of lattice strain during the hydrogenation of metals have not been sufficiently studied. This is especially important for hydrogen absorbing materials, particularly considering the fact that hydrogen, which initiates substantial crystal lattice strains [1, 4, 5], can determine changes in the physicochemical properties of such materials [2, 6–9]. The action of hydrogen on the crystal structure of membrane filters can change the degree of hydrogen purification [10, 11] and lead to the phase separation of metals absorbing hydrogen [12, 13] and failure of membranes [6, 7]. These problems cannot be solved without studying the kinetics of strain processes in hydrogenated materials. The aim of the present study is to investigate the main mechanisms of the lattice deformation of metallic alloys during secondary introduction of hydrogen into the lattice. Combined studies of the real Pd–Y–H system have been performed. The fact of practical application deserves special attention, since the hydrogen permeability of Pd–Y alloys is several time higher as compared to that of all studied palladiumbased alloys [14, 15].
EXPERIMENTAL We study diffusion foil filters 50 μm thick fabricated from a Pd94Y6 alloy, which was prepared by arc melting using high-purity metals (~99.95%). Initially, the alloy is the yttrium solid solution in palladium [16]. To ensure the homogeneity of the composition, each ingot was remelted 2–3 times. The foils were pre
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