Formation of Intermetallic Compound in Super-laminated Mg/Al Composite and its Hydrogenation Properties
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1216-W08-21
Formation of intermetallic compound in super-laminated Mg/Al composite and its hydrogenation properties Hiroshi Miyamura1, Chisa Goh1, Shiomi Kikuchi1, Nobuhiko Takeichi2, Koji Tanaka2, Hideaki Tanaka2 and Nobuhiro Kuriyama2 1 The University of Shiga Prefecture, 2500 Hassaka-cho, Hikone, Shiga 522-8533, Japan 2 AIST Kansai, 1-8-31 Midoriga-oka, Ikeda, Osaka 560-8577, Japan
ABSTRACT Compound formation properties of very finely layered Mg/Al laminate composite (“super laminate composite”) were investigated. Almost uniform Mg17Al12 compound was obtained by heat treatment of the super laminate at 673K in less than 0.6ks(10 minutes). The rate control process of the compound formation is thought to be the diffusion of Mg in Al. Hydrogenation properties of thus obtained Mg17Al12 compound were also studied and its absorption capacity and dissociation pressure were almost the same as those previously reported material, which was prepared by a longer time heat treatment. INTRODUCTION Super lamination technique is a kind of foil metallurgy[1-7]. Its process consists of repetition of stacking and rolling metal foils, finally obtaining nano-layered composite materials (“super-laminates”). Not only for reinforcement but also for preparing the precursors of sintering, super laminates are promising materials because of their very fine layered structure, which is desirable for reducing the time required for materials processing, especially those via thermal diffusion processes. We previously investigated the hydrogenation behavior of Mg17Al12 intermetallic compound prepared by this technique followed by heat treatments, and reported that they are hydrogenated via a disproportionation process[5]. In that study, it was found that almost uniform compound of Mg17Al12 was obtained in a short period of heat treatment, but the detail of how fast it was formed, how the compound formation proceeded were not clarified. In the present study, formation capability and hydrogenation properties of the Mg17Al12 intermetallic compound prepared by the super lamination technique followed by a heat treatment were investigated, and the properties were compared with the materials prepared by sintering of a mixture of Mg and Al powders. EXPERIMENTAL PROCEDURE High purity Mg and Al films with each thickness of 40µm and 20µm were stacked in alternating layers and made into a laminate composite by repetitive stacking and rolling under an ambient condition. Thus, a super laminate composite with each layer thickness less than 1µm was successfully obtained. Then the super laminate composite was subjected to heat treatment in vacuum at 673K and intermetallic compounds were synthesized. In order to study the
formation kinetics of the compounds in super laminates, some Mg/Al diffusion couples with Mo wires as the initial boundary marker were prepared. The samples were heat treated at 673 K for various periods, and the growth rates of the compounds formed on the boundary were evaluated by observation of their thickness. Intermetallic compounds were
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