Investigating the relationship between the glass-forming ability (GFA), mechanical properties, and structure of metallic glasses is crucial to understanding the nature of the metallic glass state. In this study, the correlation among the atomic structure, electronic valence band, and properties have been studied using Zr₅₀Cu_44.5−xAl_5.5Ag_x (x = 0, 1.5, 3 at.%) bulk metallic glasses (BMGs). The results reveal that through the micro-addition of Ag, the GFA of Zr₅₀Cu_44.5Al_5.5 BMG can be enhanced; meanwhile, the critical diameter of Zr₅₀Cu_44.5Al_5.5 glass rods increases from approximately 2.5 mm to 5.0 mm with the addition of 3% Ag. Through the addition of Ag, the thermal stability of Zr₅₀Cu_44.5Al_5.5 BMG is improved, and the proportion of icosahedral-like clusters increases. The plasticity of the Zr₅₀Cu_44.5−xAl_5.5Ag_x (x = 0, 1.5, 3 at.%) BMGs decreased from 4.6% to 0.8% with the addition of Ag. The valence band spectrum of the Zr₅₀Cu_44.5−xAl_5.5Ag_x (x = 0, 1.5, 3 at.%) BMGs indicates that with the addition of Ag, the p-d hybridization near the Fermi level is enhanced, and the binding energy will move to a lower value.

In this work, a small amount of Nb has been added in a Zr₅₂Cu_42.5Al_5.5 bulk metallic glass, and a Zr₅₂Cu₄₂Al_5.5Nb_0.5 bulk metallic glass composite with dual-amorphous and nanocrystal structures has been developed for the first time. This in situ formed bulk metallic glass composite has a larger room compressive plasticity of above 13% than that of the Zr₅₂Cu_42.5Al_5.5 bulk metallic glass. The excellent plasticity of the bulk metallic glass composite is attributed to the phase-separated matrix with micro-nanocrystal and the nanocrystallization during the deforming process. This work may give a new sight into design bulk metallic glass composites and the underlying mechanism for deformation.