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Severe plastic deformation (SPD) techniques are being considered as low cost processing
routes for Mg alloys, aiming hydrogen storage applications. The main objective is to develop air-
resistant materials, with lower specific surface area in comparison with ball-milled powders, but
with still attractive H-sorption kinetics associated to the microstructural refinement. In this study,
the effects of different SPD processing routes (high-pressure torsion, extensive cold rolling and cold
forging) in the hydrogen activation behavior of Mg was evaluated. The results show that both
microstructural and textural aspects should be controlled during SPD processing to obtain Mg
alloys with good H-sorption properties and enhanced activation kinetics.
Solid state hydrogen storage in metallic hydrides is a safer and more effective alternative than
the conventional methods of liquid hydrogen at cryogenic temperatures or gas under high pressures.
Among the metal hydrides, MgH
2
presents the highest gravimetric capacity of 7.6 wt% and in
addition is a cheap metal, due to its abundance. The main drawbacks for the application of
conventional (microcrystalline) Mg for hydrogen storage applications are the high temperatures
needed for H-sorption (~400 °C) and the slow kinetics involved in these processes.
Three major factors are known to control the H-sorption kinetics of Mg [1]: the grain or
crystallite size, the specific surface area of the material and the presence of additives (so-called
catalysts), e.g., transition metals, and the oxides or fluorides of these metals [2-5]. Besides this,
rapid activation (first hydrogenation) was obtained for different Mg samples, obtained by thermal
evaporation or cold rolling, and presenting [002] fibre type texture [6, 7].
Severe plastic deformation (SPD) techniques are now been explored for the preparation of
metallic materials with refined microstructures which could be adequate for hydrogen storage
applications [7 - 10]. The main advantages in this case, in comparison with ball-milled powders, are
the reduced energy and time required for processing, and the possibility of obtaining more air-
resistant materials, due to its lower specific surface area.
In the present study, we have investigated and compared the microstructural refinement, the
texture development and the hydrogen storage properties of commercial Mg processed by three
different SPD processing routes: high-pressure torsion (HPT), extensive cold rolling (CR), and
extensive cold forging (CF). The effects of the different levels of microstructural refinement and
[0002] fibre type texture development which were obtained for each SPD process used are
correlated to the hydrogen activation behavior and H-desorption kinetics.
Materials Science Forum Vols. 667-669 (2011) pp 1047-1051
Online available since 2010/Dec/30 at www.scientific.net
© (2011) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/MSF.667-669.1047
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,
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