Cluster connectivity in metallic glasses

Bulk metallic glasses were discovered more than 30 years ago. It has been established that, for multicomponent metallic glass alloys, the short-range order or the fundamental building block is characterized by solute-centered clusters [1]. Over longer length scales, the clusters are packed on a fractal network forming the medium-range order [2]. Still, there remain many questions on the structure of metallic glasses, particularly with regard to the development of short- and medium-range orders during structure evolution induced by temperature or mechanical deformation. The experimental results seem to show that during crystallization [3], mechanical deformation [4], and liquid-to-liquid phase transformation [5], the short-range order is enhanced but there are no substantial changes in the structure order. Rather, it is the connectivity between clusters at medium-range scale, that drives the dynamic response. In this paper, we explore the meaning of cluster connectivity and apply the concept to explain our experimental observations.