Mechanical relaxation in supercooled liquids of bulk metallic glasses

Abstract

We report the mechanical relaxation behaviors in typical supercooled liquids of bulk metallic glasses (BMGs). The metallic supercooled liquids are ideal systems for studying intrinsic motions of glass‐former supercooled liquids because their structure is close to the simple “dense random packing of spheres” model. We show that the primary relaxation in the frequency domain is dissipative and can be described by the empirical Kohlrausch–Williams–Watts function, and the temperature dependence of the primary relaxation time has the Vogel–Fulcher–Tamman form. Beyond the primary relaxation, an excess wing is found on the high‐frequency tail of the primary relaxation. A corresponding shoulder is exhibited at a given frequency in the temperature region below the glass‐transition temperature. The experimental results confirm that the decoupling between the slow β relaxation and the primary (α) relaxation exists in metallic supercooled liquids. Based on the current models of the glass transition, we demonstrate that the dynamically heterogeneity originates in the heterogeneous microstructure of metallic supercooled liquids, and a picture of the heterogeneous microstructure is provided.

Dynamic mechanical analysis in La-based bulk metallic glasses: Secondary (β) and main (α) relaxations

“…24 In contrast, many metallic glasses do not exhibit any obvious b relaxation, 13,14 while in some cases a distant b relaxation has been observed by mechanical spectroscopy technique: in Pd-based, 13,[25][26][27] La-based, [28][29][30] Ce-based, 31 and Nd 65 Fe 15 Co 10 Al 10 32 metallic glasses.…”

Specific volume study of a bulk metallic glass far below its calorimetrically determined glass transition temperature

“…Usually in DMA experiments the frequency or temperature dependent elastic moduli are studied and the structural relaxation time is determined. However, this is only possible if the structure of the glass is in equilibrium at any time of the experiment, i.e., the material must exhibit a liquidlike behavior and therefore these measurements are limited to higher temperatures, usually above T g [18][19][20][21].…”

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