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To uncover the structural origins of composition-dependent ductility in amorphous alloys, the authors mapped multiscale medium-range order (MRO) across five Zr-based metallic glasses by combining synchrotron reduced density function $G(r)$ analysis with machine-learning-assisted 4D-STEM. Bridging geometric density correlations with nanoscale topological symmetry resolves a persistent bottleneck in explaining macroscopic mechanical relaxation in disordered solids. The findings reveal that while $G(r)$ coherence lengths define the baseline volume for cooperative shear, ductility is actively enhanced when higher Zr content suppresses embrittling Cu-rich FCC-like motifs and promotes fine Zr-rich HCP-like local ordering.
Metallic glass brittleness stems from hidden nanoscale crystalline motifs: machine learning on 4D-STEM diffraction data reveals that replacing Cu-rich FCC-like ordering with fine Zr-rich HCP-like clusters directly dictates ductile relaxation.
Metallic glasses exhibit pronounced composition-dependent mechanical properties, yet identifying the structural origins of these changes remains difficult. An outstanding issue is how to correlate different forms of medium range order (MRO), defined at different length scales and accessed through different experimental observables, and to understand their connection to properties. We combine synchrotron reduced density function, G(r), with machine-learning-assisted four dimensional scanning transmission electron microscopy (4D-STEM) to examine geometric and topological MRO in five Zr-based metallic glasses. Density wave analysis of G(r) provides a geometric MRO descriptor through the coherence length of atomic density correlations, while 4D-STEM reveals nanoscale topological and chemical MRO motifs, including crystal-like local ordering with distinct rotational symmetries. We show that the G(r)-derived coherence length captures an important baseline tendency for cooperative ductile relaxation, while composition-dependent topological MRO provides an additional structural contribution that helps explain the observed mechanical responses. In particular, increasing Zr content suppresses Cu-rich FCC-like MRO, increases the cooperative coherence volume, and promotes fine Zr-rich HCP-like local order associated with enhanced ductility. These results identify the combined structural influence of geometric and topological MRO as a key basis for composition-dependent mechanical response in metallic glasses.