Dissimilar nanoscaled structural heterogeneity in U-based metallic glasses revealed by nanoindentation

Abstract Nanoscaled structure inhomogeneity has been identified to be an inherent characteristic of metallic glasses (MGs). Structural heterogeneities are also found to play a key role in designing and tuning the mechanical and relaxation behavior of MGs. As one peculiar member of the glassy family, U-based MGs show novel unique properties desirable for nuclear industries. However, the heterogeneous characteristics of this type of MGs have never been studied so far. In this study, U 65 Fe 30 Al 5 and U 60 Fe 27.5 Al 12.5 MGs were systematically investigated with nanoindentation of high sensitivity. They exhibit significantly different mechanical response for the primary and secondary creeps at varying loading rates and peak loads. Through analysis with the theoretical creep model for viscoelastic materials, U 60 Fe 27.5 Al 12.5 MG is found to be in a more rigid state for the secondary (viscous) creep, suggesting more compact atomic structure for it. By further analysis and fitting with this model, dissimilar structural heterogeneity can be derived for these two MGs to account for their difference in creeping behavior. This work manifests that nanoindentation is a very useful technique to reveal heterogeneous structures of glassy alloys, and also to establish their composition-structure-property relationship.