Deformation zone connectivity governs time-dependent load relaxation in Cu-Zr-based metallic glasses

Metallic glasses (MGs) are used in contact-fatigue applications, where damage develops through time-dependent subsurface plasticity. Indentation hold tests quantify this response through load relaxation, yet relaxation alone cannot disentangle the underlying deformation modes nor reveal the influence of alloy chemistry and structural state. Here, large-scale molecular dynamics simulations were used to examine indentation hold response in Cu-Zr-based MG series, spanning binary to quinary compositions, namely Cu 50 Zr 50 , Cu 45 Zr 48 Al 7 , Cu 39 Zr 46 Al 7 Ag 8 , and Cu 37 Zr 42 Al 7 Ag 8 Ti 6 , across three structural states. The results show that the indentation depth-hold response is governed by structure-influenced deformation-zone connectivity rather than the activated population alone. Annealing reduces the free volume content and increases local packing constraints, lowering both the activated population and its coalescence into a dominant, connected active zone during the hold. Increasing compositional complexity produces the same overall tendency. To compare these coupled structural changes on a common basis, a disorder partition metric, Π ⁎ , is introduced as a compact descriptor of the balance between free volume-dominated disorder and packing stabilization. Larger Π ⁎ is associated with lower active zone connectivity and weaker force relaxation, whereas smaller Π ⁎ is associated with greater coalescence of the plastically activated population and stronger relaxation during the hold. These results establish comparative atomistic trends in indentation hold deformation for Cu-Zr-(Al/Ag/Ti) MGs and show that interpreting load relaxation requires simultaneous consideration of the compositional complexity, structural state, and the plastic zone connectivity. • Plastic zone connectivity governs indentation hold relaxation in Cu-Zr-based MGs. • Load relaxation alone does not resolve the underlying deformation mode. • Π ⁎ links free volume reduction to packing stabilization across MG structural states. • Annealing and alloy compositional complexity suppress active zone coalescence.