Influence of topological structure and chemical segregation on the thermal and mechanical properties of Pd-Si nanoglasses

Metallic nanoglasses are non-crystalline solids with interfacial regions, typically characterized by a modified short-range order and compositional gradients. These interfaces can act as nucleation sites for the formation of shear transformation zones during mechanical deformation, which gives rise to a deformation behavior distinct from the bulk glass counterpart. While various studies have investigated nanoglasses experimentally (mostly Fe-Sc) and in computer simulations (typically Cu-Zr), there is hitherto no study comparing compositionally identical nanoglasses and conventional metallic glasses by experiments and simulations. In this contribution, we investigate Pd-Si as a model system and compare nanoglasses produced by inert gas condensation with melt-spun ribbons. Molecular dynamics simulations and atom probe tomography provide evidence that glass-glass interfaces are primarily topological and chemical defects in this particular system. Differential scanning calorimetry shows a decrease in the glass transition and crystallization temperature of the nanoglasses compared to melt-spun ribbons. Nanoindentation and micropillar tests on Pd-Si metallic nanoglasses, however, provide evidence for shear band formation in both sample types, the melt-spun ribbons and nanoglass. Shear bands in the nanoglass samples appear more diffuse as compared to melt-spun ribbons. This is also evident from the reduced strain localization in the nanoglass. It is concluded that the topological inhomogenieties induced by forming glass-glass interfaces significantly affect the mechanical properties of nanoglasses. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.