Regensburg 2007 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 3: Liquid and amorphous materials I

MM 3.2: Vortrag

Montag, 26. März 2007, 10:30–10:45, H4

Interplay of Structure and Dynamics in liquid and undercooled AlNi melts — •Sebastian Stüber¹, Andreas Meyer², Dirk Holland-Moritz², Helena Hartmann², and Tobias Unruh³ — ¹Physik Department E13, TU München — ²Institut für Materialphysik im Weltraum, DLR Köln — ³Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Garching

AlNi melts show a chemical short-range order (CSRO), dependent on the Ni concentration [1]. For lower temperatures, this CSRO becomes more pronounced. To increase the available temperature range further, we used electromagnetic levitation. This container-free method enabled significant undercooling (up to 266 K) for several hours.

The AlNi melts were studied using inelastic neutron scattering. The quasielastic line was fitted by a scaled Lorentzian, whose HWHM corresponds to the inverse of the mean relaxation time τ_q. With this a q-dependent diffusivity D(q)=1/(τ q²) can be defined, for the hydrodynamic limit q → 0 one gets the (Ni) self-diffusion coefficient D as a function of temperature.

The q-dependent diffusivity D(q) provides information about the correlation between the diffusive motion and the CSRO, visible at intermediate q values. Using D(q) we will discuss the process of diffusive atomic motion in AlNi melts, under the pronounced influence of CSRO.

[1] S.K. Das et al., Appl. Phys. Lett. 86, 011918 (2005).