Evaluation of flow units and free volumes in metallic glasses

We investigate the changes of the fractions of flow units and free volumes in two typical metallic glasses by variation of their preparation cooling rates. It is found that the fractions of the flow units and the free volumes show a similar dependence on the cooling rate, which is suggestive of the existence of a strong connection between them. The microstructural correlation between flow units and free volumes of the metallic glasses is discussed, which could be helpful for understanding the formation and structural features of the flow units as well as their effects on mechanical properties and relaxation behaviors in metallic glasses.