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MM: Fachverband Metall- und Materialphysik

MM 11: Topical Session Glass Dynamics IV

MM 11.3: Vortrag

Montag, 22. März 2010, 17:00–17:15, H16

Thermodynamics and kinetics of glass transition during structural ordering of Fe50Co50 — •Shuai Wei¹, Isabella Gallino¹, Ralf Busch¹, and Austen Angell² — ¹Department of Materials Science and Engineering, Saarland University, 66123 Saarbrücken, Germany — ²Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85278, USA

The glass transition is not only the formation of an amorphous material from a supercooled liquid, but also, in general, the ergodicity-breaking of a system during a kinetic slow down process like cooling (i.e. freezing-in). Therefore, there are various kinds of glasses, conventional glasses (e.g. SiO2), spin glasses and orientational glasses...

Here we report a glass-like transition event that occurs in a simple crystalline alloy Fe50Co50 during the order-disorder transition (lambda transition). By studying the thermodynamics and kinetics of this glass-like transition, we identify the transition as a glass transition with respect to ordering of this crystalline system. The structural relaxation times as a function of temperature are fitted with the Arrhenius law and the VFT equation. The results show that the kinetics of Fe50Co50 is simple Arrhenius. We also show that the enthalpy relaxation function evolving with time is non-exponential. By comparing the glass transition of Fe50Co50 with the strong glass-formers, BeF2 and SiO2, we found that they have great similarity in heat capacity behaviour and the change in entropy. Additionally, the study solves the old problem of the incomprehensible kinks in the tail of lambda transition peak in the heat capacity curves of of β-brass and Cu3Au.