Quenched-in liquid in glass

Glasses have long been considered as frozen liquids because of the similarity between their static amorphous structures. While the modern theories about glass transition suggest that glass transition may result from supercooling of a heterogeneous liquid that contains fast and slow regions, it remains unclear whether such a physical picture applies to metallic glasses, which are a densely packed solid glass that was once believed to be a vitrified homogeneous metallic liquid. However, in the recent work published in Nature Materials, Chang et al provide compelling evidence to show that metallic glasses contain liquid-like atoms that behave as a high-temperature liquid in stress relaxation. Being activated under cyclic loading, this quenched-in liquid results in a fast relaxation process, which is discovered in a variety of metallic glasses. Their results are important and deliver a strong message that metallic glasses have a dynamic microstructure containing liquid- and solid-like atoms. Most importantly, the outcome of their research provides physical insight into the nature of glass-transition in metallic glasses, and also helps unravel their structure-property relations.