Probing nano-scale heterogeneities in metallic glasses

We propose to study nano-scale density inhomogeneities in metallic glasses (MGs) and how they relate to the stability and mechanical properties of the glasses, using nano-tomography at ID16A. Recent studies have shown that density inhomogeneities on the length scale of ~100nm and up to 20% in magnitude exist in melt-quenched MGs. On the other hand, a family of vapor-deposited MGs have been found to exhibit a greater stability and an enhanced mechanical uniformity, but it remains to be seen how their structure differs on the nanoscale. In particular, it is unknown whether density inhomogeneities exist in these ultra-stable MGs, and if so, what is the level and length scale. Phase-contrast X-ray tomography at ID16A is well suited to answer this question thanks to its capability to detect low-level electron density fluctuations. The results are relevant to both the physical nature of the glass transition and industrial applications based on the mechanical properties of MGs.