Comparative analysis of plastic deformation in Zr-Cu-Ag metallic glasses across macro and micro scales: Insights from micropillar and bulk sample compression tests of fully and partially amorphous alloy

This study compared the mechanical behaviour of fully amorphous Zr 50 Cu 37 Ag 13 and partially amorphous Zr 42 Cu 40 Ag 18 alloys at both micro- and macroscales using micropillar and bulk compression tests. Both alloys were synthesised via arc melting and tested at strain rates ranging from 10⁻⁴ to 10⁻¹ s⁻¹. Micropillar tests revealed significant plastic deformation accompanied by serrated flow, with yield strengths ranging from 1468 to 1590 MPa for Zr 50 Cu 37 Ag 13 and from 1512 to 1758 MPa for Zr 42 Cu 40 Ag 18 . In contrast, bulk tests exhibited limited plasticity. The Zr 42 Cu 40 Ag 18 alloy fractured in a brittle manner, attributed to the presence of the crystalline Zr₂Ag phase. Negative strain rate sensitivity (SRS) was observed in all micropillar tests and in the bulk Zr 50 Cu 37 Ag 13 samples, whereas the Zr 42 Cu 40 Ag 18 bulk samples displayed positive SRS. Analysis of serrated flow in the micropillars revealed pronounced stress drops (Δσ), which increased with decreasing strain rate, indicating active shear band formation and propagation. The negative SRS was attributed to adiabatic shear banding, whereby localised heat generation at high strain rates softened the material and facilitated shear band formation. In contrast, the positive SRS observed in Zr 42 Cu 40 Ag 18 bulk samples was likely a result of the Zr₂Ag phase, which reduced deformation localisation, promoted a more uniform stress distribution, and activated additional plasticity mechanisms. The smaller stress drops observed in bulk samples stemmed from more dispersed deformation and improved heat dissipation, in contrast to the highly localised deformation seen in micropillars. Fractographic analysis revealed vein-like patterns in Zr 50 Cu 37 Ag 13 and mixed features in Zr 42 Cu 40 Ag 18 , highlighting the influence of sample size and composition on mechanical behaviour. • Bulk Zr50Cu37Ag13 shows ductility, while Zr42Cu40Ag18 fractures due to Zr₂Ag phase. • Negative SRS in micropillars ties to adiabatic shear banding and localized heat softening. • Serrated flows show strain-rate-dependent stress drops in micropillars and bulk samples.