Facilitation and correlation of flow in metallic supercooled liquid.

Elucidation of the flow mechanism of the supercooled liquid near the glass transition temperature Tg is crucial for understanding the nature of glass transition. Dynamic facilitation between adjacent flow events in the supercooled liquid is believed to be crucial in the process of glass transition. In this work, it is shown that shear dilatation-based dynamic facilitation plays an important role in the supercooled liquid state of Zr58.5Cu15.6Al10.3Ni12.8Nb2.8, as revealed by the observed strain rate softening in the stress-strain curves above Tg = 684 K. Interestingly, along with strain rate softening, damped oscillations in the stress-strain curve emerge below 713 K, suggesting large-scale correlation between flow events as temperature approaches Tg. Such oscillations are absent above 713 K although strain rate softening remains even at 733 K. Analysis indicates that facilitation and correlation are both crucial for the flow of metallic supercooled liquid approaching Tg.