Berlin 2005 – wissenschaftliches Programm

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M: Metallphysik

M 2: Flüssige und amorphe Metalle I

M 2.2: Vortrag

Freitag, 4. März 2005, 10:45–11:00, TU H111

Reversible formation and disappearance of free volumes in a bulk metallic glass — •W. Sprengel¹, F. Ye^1,2, R.K. Wunderlich³, H.-J. Fecht³, H. Dosch², and H.-E. Schaefer¹ — ¹Universität Stuttgart, Institut für Theoretische und Angewandte Physik, Stuttgart, Germany — ²Max-Planck-Institut für Metallforschung, Stuttgart, Germany — ³Universität Ulm, Materials Division, Ulm, Germany

In the bulk metallic glass Zr₅₇Cu_15.4Ni_12.8Nb₅Al₁₀ the reversible formation and disappearance of free volumes have been detected by time-differential dilatometry studies in analogy to the observation of thermal vacancy formation in B2-intermetallics (H.-E. Schaefer et al., PRL 82, 948 (1999)). After an initial long-term annealing of the bulk amorphous system at 593 K cycles of fast temperature changes have been carried out below the glass temperature T_g = 672 K and subsequent time-dependent reversible elongation after fast heating or shrinking after fast cooling has been observed by isothermal interferometric dilatometry. During these processes no changes of the amorphous structure were detected. This demonstrates that free volumes are reversibly formed or disappear in a deeply metastable structure. The kinetics of the time-dependent process indicate that an entire ensemble of atoms is involved in the thermal formation of free volumes in the bulk amorphous solid.