Structural Heterogeneity, Ductility, and Glass Forming Ability of Zr-Based Metallic Glasses

We show the correlation between nanoscale structural heterogeneity, mechanical property, and glass-forming ability of Zr-Cu-Co-Al metallic glasses (MGs). Local regions with medium-range ordering (MRO) were directly visualized in electron dark-field images of (Zr 45 Cu 50 Al 5 ) 1- x (Zr 55 Co 25 Al 20 ) x MGs acquired using 4-dimensional scanning transmission electron microscopy (4D-STEM), which enables determination of the type, size, and volume fraction of MRO domains with high precision and statistical reliability. Angular correlation analysis of 4D-STEM data shows notable differences in MRO types between x = 0 and x = 1, and certain types of MRO involve structural frustration that correlates to high glass-forming ability. More importantly, the smaller and more diverse MRO at x = 0.5 correlates with a substantial increase in ductility, suggesting a potential role of MRO in the deformation of MGs. Mesoscale deformation simulation incorporating the experimentally determined MRO confirms that the diverse types and sizes of MRO can significantly influence the MGs’ mechanical behavior, which we attribute to the strain frustration mechanism due to increased heterogeneity.