Size-dependent vitrification in metallic glasses

The sample size dependence of the glass transition in metallic glasses has hitherto remained elusive. Here, the authors show that, reducing sample size below 10 & mu;m, the glass transition temperature can be depressed by as much as 40 K, thereby allowing attaining glasses with low energy states. Reducing the sample size can profoundly impact properties of bulk metallic glasses. Here, we systematically reduce the length scale of Au and Pt-based metallic glasses and study their vitrification behavior and atomic mobility. For this purpose, we exploit fast scanning calorimetry (FSC) allowing to study glassy dynamics in an exceptionally wide range of cooling rates and frequencies. We show that the main & alpha; relaxation process remains size independent and bulk-like. In contrast, we observe pronounced size dependent vitrification kinetics in micrometer-sized glasses, which is more evident for the smallest samples and at low cooling rates, resulting in more than 40 K decrease in fictive temperature, T-f, with respect to the bulk. We discuss the deep implications on how this outcome can be used to convey glasses to low energy states.