Mechanical Spectroscopy of the Formation of Quasicrystalline Order in Rapidly Quenched Ti- and Zr-based Alloys
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Mechanical Spectroscopy of the Formation of Quasicrystalline Order in Rapidly Quenched Ti- and Zr-based Alloys Hans-Rainer Sinning, Igor S. Golovin, and Adrian Jianu1 Institute for Materials, Technical University of Braunschweig, Langer Kamp 8, 38106 Braunschweig, Germany. 1 National Institute of Materials Physics, Bucharest-Magurele, Romania ABSTRACT The development of quasicrystalline (qc) order from different initial states (amorphous, nano- or poly-qc) was studied in rapidly quenched Ti-Zr-Ni(-Ag), Ti-Zr-Fe, and Zr-Cu-Ni-Al alloys by means of mechanical spectroscopy (vibrating-reed technique), including both the irreversible changes of Young’s modulus and the Snoek-type relaxation peak of absorbed hydrogen as a probe, which are obviously sensitive to quite different types of ordering processes. The strongest annealing effects on Young’s modulus were found for extreme nano-qc material at the amorphous limit, whereas order-induced narrowing of the hydrogen peak occurs only at comparatively larger grain sizes. More important differences in the properties of the hydrogen peak are found between quasicrystals of different compositions. The results are briefly discussed with respect to their implications for the amorphous-to-quasicrystalline transition and for the experimental distinction between different types of icosahedral quasicrystalline order.
INTRODUCTION Mechanical spectroscopy is concerned with the elastic as well as with the dissipative parts of the mechanical response of a solid to a mechanical perturbation. Both these parts are valuable not only as engineering properties (elastic moduli, damping of vibrations) to characterize the mechanical behavior of a material, but also as sensitive tools to study structural transformations and defects in solids. Previous applications of mechanical spectroscopy to quasicrystals were directed e.g. to elastic constants and elastic isotropy [1,2], to a search for phasonic defects both in the low [3] and high [4] temperature regimes, and to the Snoek-type relaxation of absorbed hydrogen [57] (see [6,7] for a more complete literature survey). The latter effect, also known for amorphous and crystalline phases, is directly sensitive to local atomic order using hydrogen as a probe [810], which gives an additional possibility of studying aspects of short-range order in H-absorbing quasicrystals [5-7]. If icosahedral quasicrystals are prepared via the rapid quenching route, a non-equilibrium, more or less defective state is produced which tends to transform to a more ordered, stable or metastable quasicrystalline state. These ordering processes may influence the different quantities of mechanical spectroscopy in different ways, which led us in the present work to combine Young’s modulus and the Snoek-type peak of hydrogen to see different aspects of the ordering processes simultaneously. Part of the results on different Ti-Zr-Ni(-Ag) alloys, also interesting for H storage applications [11,12], have already been considered under the viewpoint of the amorphous-quasicrysta
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