Dresden 2006 – wissenschaftliches Programm

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MM: Metall- und Materialphysik

MM 36: Amorphous and Liquid Materials IV

MM 36.6: Vortrag

Donnerstag, 30. März 2006, 17:45–18:00, IFW B

Positron annihilation spectroscopy of glassy Mg₆₅Cu₂₅Y₁₀ ribbons — •Dirk I. Uhlenhaut¹, Alberto Castellero¹, Florian Dalla Torre¹, Carlos Palacio², Nikolay Djourelov², Danny Segers², and Jörg F. Löffler¹ — ¹Laboratory of Metal Physics and Technology, Swiss Federal Institute of Technology (ETH) Zürich, Wolfgang-Pauli-Str. 10, CH-8093 Zürich, Switzerland — ²Department of Subatomic and radiation physics, Gent University, Proeftuinstraat 86, B-9000 Gent, Belgium

The well-known Mg-Cu-Y amorphous alloys become brittle during quenching or ageing. The ductile state is obtained at high quenching speeds, while a low copper content delays embrittlement during room-temperature ageing. Here we report on positron annihilation spectroscopy of amorphous ribbons from the Mg₆₅Cu₂₅Y₁₀ bulk glass-former, measuring positron lifetime, Doppler broadening and coincidence Doppler broadening as a function of the alloy’s room temperature age. A decrease in positron lifetime and changes in the Doppler peak width, corresponding to a reduction of free volume, were seen during the time the embrittlement takes place at room temperature. Coincidence Doppler broadening spectroscopy revealed changes in the immediate environment of the free volume during annihilation. Analogies with calorimetric measurments and mechanical tests are discussed.