Regensburg 2013 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 65: Liquid & Amorphous Metals II
MM 65.2: Vortrag
Donnerstag, 14. März 2013, 17:30–17:45, H26
Decoupling of component diffusivities in glass-forming Zr-Ni-Ti-Cu-Be alloys above the melting temperature — •Sri Wahyuni Basuki1, Fan Yang2, Andreas Meyer2, Klaus Rätzke1, and Franz Faupel1 — 1Faculty of Engineering, Kiel, Germany — 2Inst. of Materials Physics in Space, Köln, Germany
Previous work[1] on glass forming Pd-Cu-Ni-P alloys, showed that while a vast decoupling occurs between the diffusivity of Pd and of the smaller components, the diffusivities of all components merge close to the critical temperature Tc of mode coupling theory. For Pd, the Stokes-Einstein relation holds in the whole range investigated encompassing more than 14 orders of magnitude. In order to check for the general validity of these results, we extended our investigations to the Zr-Cu-Ni-Ti-Be system. In this work, Co-57 and Zr-95 tracer diffusivities were determined in glass-forming Zr46.75Ti8.25Cu7.5Ni10Be27.5 above the melting temperature. In particular, measurements were carried out simultaneously to minimize artefacts from diffusion barriers and to reduce absolute errors. Even at 20 K above the liquidus temperature, the diffusivities of Zr and Co differ clearly by a factor of four, while Co tracer diffusivities agree very well with diffusivities determined by quasielastic neutron scattering. This together with measurements of the time dependence of the penetration profiles demonstrates the general reliability of the measurements. The results are discussed in connection with viscosity data and the Stokes-Einstein equation in terms of imperfect equilibration of the melt.
[1] A. Bartsch et al., Phys. Rev. Lett. 104, 195901 (2010).