Effects of minor-alloying on plasticity in metallic glasses: Correlations with structural heterogeneity

Minor alloying is a promising strategy for enhancing the mechanical performance of metallic glasses (MGs), yet the effects of specific elements on structure and properties remain poorly understood. Here, using molecular dynamics simulations of Zr–Cu MGs alloyed with Al and Ag, we show that these elements induce opposing structural responses due to distinct chemical affinities. Al increases strength but promotes embrittlement through strong Cu–Al and Al–Al bonding across short and medium ranges, while Ag weakens strength and improves ductility through weak Cu–Ag interactions and Ag clustering. Structural analyses reveal that medium-range connectivity, rather than short-range order or local flexibility volume, governs strain localization and shear band formation. These insights highlight the critical role of medium-range order in controlling plasticity and offer a framework for designing compositions with improved strength-ductility synergy.