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Viscous flow of Fe82B18 amorphous alloy under continuous heating conditions

1990; Elsevier BV; Volume: 123; Issue: 1 Linguagem: Inglês

10.1016/0921-5093(90)90210-t

1873-4936

Krassimir Russew, Liljana Stojanova,

Phase-change materials and chalcogenides

Viscous flow measurements were carried out on Fe82B18 amorphous alloy with the aid of a Perkin-Elmer TMS-2 thermomechanical analyser under constant heating rate conditions through the glass transition temperaure (Tg ≈ 710 K) and during the course of crystallization. Two Arrhenius-type temperature dependences of the viscosity in the temperature ranges (Tg − 80) K to Tg and Tg to Fg + 30 K were observed, yielding activation energies for viscous flow of 49–55 kJ mol−1 and 230–240 kJ mol−1 respectively. In the temperature range Tg−Tm the temperature dependence of the viscosity is described more realistically by the Vogel-Fulcher-Tamman (VFT)-type empirical relations. The molar heat of fusion ΔHm (10 kJ mol−1) and the melting temperature Tm (1440 K) of the alloy were also measured. These parameters were used to calculate the critical cooling rate needed to avoid crystallization via the standard nucleation-crystal growth-volume transformation theory. The critical cooling rate estimated on the basis of VFT-temperature dependences of η was approximately 106 K s−1, in good agreement with the experimental evidence.